Source code: Lib/codecs.py
This module defines base classes for standard Python codecs (encoders and decoders) and provides access to the internal Python codec registry, which manages the codec and error handling lookup process. Most standard codecs are text encodings, which encode text to bytes, but there are also codecs provided that encode text to text, and bytes to bytes. Custom codecs may encode and decode between arbitrary types, but some module features are restricted to use specifically with text encodings, or with codecs that encode to bytes.
The module defines the following functions for encoding and decoding with any codec:
Encodes obj using the codec registered for encoding.
Errors may be given to set the desired error handling scheme. The default error handler is 'strict' meaning that encoding errors raise ValueError (or a more codec specific subclass, such as UnicodeEncodeError). Refer to Codec Base Classes for more information on codec error handling.
Decodes obj using the codec registered for encoding.
Errors may be given to set the desired error handling scheme. The default error handler is 'strict' meaning that decoding errors raise ValueError (or a more codec specific subclass, such as UnicodeDecodeError). Refer to Codec Base Classes for more information on codec error handling.
The full details for each codec can also be looked up directly:
Looks up the codec info in the Python codec registry and returns a CodecInfo object as defined below.
Encodings are first looked up in the registry’s cache. If not found, the list of registered search functions is scanned. If no CodecInfo object is found, a LookupError is raised. Otherwise, the CodecInfo object is stored in the cache and returned to the caller.
Codec details when looking up the codec registry. The constructor arguments are stored in attributes of the same name:
The name of the encoding.
The stateless encoding and decoding functions. These must be functions or methods which have the same interface as the encode() and decode() methods of Codec instances (see Codec Interface). The functions or methods are expected to work in a stateless mode.
Incremental encoder and decoder classes or factory functions. These have to provide the interface defined by the base classes IncrementalEncoder and IncrementalDecoder, respectively. Incremental codecs can maintain state.
Stream writer and reader classes or factory functions. These have to provide the interface defined by the base classes StreamWriter and StreamReader, respectively. Stream codecs can maintain state.
To simplify access to the various codec components, the module provides these additional functions which use lookup() for the codec lookup:
Look up the codec for the given encoding and return its encoder function.
Raises a LookupError in case the encoding cannot be found.
Look up the codec for the given encoding and return its decoder function.
Raises a LookupError in case the encoding cannot be found.
Look up the codec for the given encoding and return its incremental encoder class or factory function.
Raises a LookupError in case the encoding cannot be found or the codec doesn’t support an incremental encoder.
Look up the codec for the given encoding and return its incremental decoder class or factory function.
Raises a LookupError in case the encoding cannot be found or the codec doesn’t support an incremental decoder.
Look up the codec for the given encoding and return its StreamReader class or factory function.
Raises a LookupError in case the encoding cannot be found.
Look up the codec for the given encoding and return its StreamWriter class or factory function.
Raises a LookupError in case the encoding cannot be found.
Custom codecs are made available by registering a suitable codec search function:
Register a codec search function. Search functions are expected to take one argument, being the encoding name in all lower case letters with hyphens and spaces converted to underscores, and return a CodecInfo object. In case a search function cannot find a given encoding, it should return None.
Changed in version 3.9: Hyphens and spaces are converted to underscore.
Note
Search function registration is not currently reversible, which may cause problems in some cases, such as unit testing or module reloading.
While the builtin open() and the associated io module are the recommended approach for working with encoded text files, this module provides additional utility functions and classes that allow the use of a wider range of codecs when working with binary files:
Open an encoded file using the given mode and return an instance of StreamReaderWriter, providing transparent encoding/decoding. The default file mode is 'r', meaning to open the file in read mode.
Note
Underlying encoded files are always opened in binary mode. No automatic conversion of '\n' is done on reading and writing. The mode argument may be any binary mode acceptable to the built-in open() function; the 'b' is automatically added.
encoding specifies the encoding which is to be used for the file. Any encoding that encodes to and decodes from bytes is allowed, and the data types supported by the file methods depend on the codec used.
errors may be given to define the error handling. It defaults to 'strict' which causes a ValueError to be raised in case an encoding error occurs.
buffering has the same meaning as for the built-in open() function. It defaults to -1 which means that the default buffer size will be used.
Return a StreamRecoder instance, a wrapped version of file which provides transparent transcoding. The original file is closed when the wrapped version is closed.
Data written to the wrapped file is decoded according to the given data_encoding and then written to the original file as bytes using file_encoding. Bytes read from the original file are decoded according to file_encoding, and the result is encoded using data_encoding.
If file_encoding is not given, it defaults to data_encoding.
errors may be given to define the error handling. It defaults to 'strict', which causes ValueError to be raised in case an encoding error occurs.
Uses an incremental encoder to iteratively encode the input provided by iterator. This function is a generator. The errors argument (as well as any other keyword argument) is passed through to the incremental encoder.
This function requires that the codec accept text str objects to encode. Therefore it does not support bytes-to-bytes encoders such as base64_codec.
Uses an incremental decoder to iteratively decode the input provided by iterator. This function is a generator. The errors argument (as well as any other keyword argument) is passed through to the incremental decoder.
This function requires that the codec accept bytes objects to decode. Therefore it does not support text-to-text encoders such as rot_13, although rot_13 may be used equivalently with iterencode().
The module also provides the following constants which are useful for reading and writing to platform dependent files:
These constants define various byte sequences, being Unicode byte order marks (BOMs) for several encodings. They are used in UTF-16 and UTF-32 data streams to indicate the byte order used, and in UTF-8 as a Unicode signature. BOM_UTF16 is either BOM_UTF16_BE or BOM_UTF16_LE depending on the platform’s native byte order, BOM is an alias for BOM_UTF16, BOM_LE for BOM_UTF16_LE and BOM_BE for BOM_UTF16_BE. The others represent the BOM in UTF-8 and UTF-32 encodings.
The codecs module defines a set of base classes which define the interfaces for working with codec objects, and can also be used as the basis for custom codec implementations.
Each codec has to define four interfaces to make it usable as codec in Python: stateless encoder, stateless decoder, stream reader and stream writer. The stream reader and writers typically reuse the stateless encoder/decoder to implement the file protocols. Codec authors also need to define how the codec will handle encoding and decoding errors.
To simplify and standardize error handling, codecs may implement different error handling schemes by accepting the errors string argument. The following string values are defined and implemented by all standard Python codecs:
Value
Meaning
'strict'
Raise UnicodeError (or a subclass); this is the default. Implemented in strict_errors().
'ignore'
Ignore the malformed data and continue without further notice. Implemented in ignore_errors().
The following error handlers are only applicable to text encodings:
Value
Meaning
'replace'
Replace with a suitable replacement marker; Python will use the official U+FFFD REPLACEMENT CHARACTER for the built-in codecs on decoding, and ‘?’ on encoding. Implemented in replace_errors().
'xmlcharrefreplace'
Replace with the appropriate XML character reference (only for encoding). Implemented in xmlcharrefreplace_errors().
'backslashreplace'
Replace with backslashed escape sequences. Implemented in backslashreplace_errors().
'namereplace'
Replace with \N{...} escape sequences (only for encoding). Implemented in namereplace_errors().
'surrogateescape'
On decoding, replace byte with individual surrogate code ranging from U+DC80 to U+DCFF. This code will then be turned back into the same byte when the 'surrogateescape' error handler is used when encoding the data. (See PEP 383 for more.)
In addition, the following error handler is specific to the given codecs:
Value
Codecs
Meaning
'surrogatepass'
utf-8, utf-16, utf-32, utf-16-be, utf-16-le, utf-32-be, utf-32-le
Allow encoding and decoding of surrogate codes. These codecs normally treat the presence of surrogates as an error.
New in version 3.1: The 'surrogateescape' and 'surrogatepass' error handlers.
Changed in version 3.4: The 'surrogatepass' error handlers now works with utf-16* and utf-32* codecs.
New in version 3.5: The 'namereplace' error handler.
Changed in version 3.5: The 'backslashreplace' error handlers now works with decoding and translating.
The set of allowed values can be extended by registering a new named error handler:
Register the error handling function error_handler under the name name. The error_handler argument will be called during encoding and decoding in case of an error, when name is specified as the errors parameter.
For encoding, error_handler will be called with a UnicodeEncodeError instance, which contains information about the location of the error. The error handler must either raise this or a different exception, or return a tuple with a replacement for the unencodable part of the input and a position where encoding should continue. The replacement may be either str or bytes. If the replacement is bytes, the encoder will simply copy them into the output buffer. If the replacement is a string, the encoder will encode the replacement. Encoding continues on original input at the specified position. Negative position values will be treated as being relative to the end of the input string. If the resulting position is out of bound an IndexError will be raised.
Decoding and translating works similarly, except UnicodeDecodeError or UnicodeTranslateError will be passed to the handler and that the replacement from the error handler will be put into the output directly.
Previously registered error handlers (including the standard error handlers) can be looked up by name:
Return the error handler previously registered under the name name.
Raises a LookupError in case the handler cannot be found.
The following standard error handlers are also made available as module level functions:
Implements the 'strict' error handling: each encoding or decoding error raises a UnicodeError.
Implements the 'replace' error handling (for text encodings only): substitutes '?' for encoding errors (to be encoded by the codec), and '\ufffd' (the Unicode replacement character) for decoding errors.
Implements the 'ignore' error handling: malformed data is ignored and encoding or decoding is continued without further notice.
Implements the 'xmlcharrefreplace' error handling (for encoding with text encodings only): the unencodable character is replaced by an appropriate XML character reference.
Implements the 'backslashreplace' error handling (for text encodings only): malformed data is replaced by a backslashed escape sequence.
Implements the 'namereplace' error handling (for encoding with text encodings only): the unencodable character is replaced by a \N{...} escape sequence.
New in version 3.5.
The base Codec class defines these methods which also define the function interfaces of the stateless encoder and decoder:
Encodes the object input and returns a tuple (output object, length consumed). For instance, text encoding converts a string object to a bytes object using a particular character set encoding (e.g., cp1252 or iso-8859-1).
The errors argument defines the error handling to apply. It defaults to 'strict' handling.
The method may not store state in the Codec instance. Use StreamWriter for codecs which have to keep state in order to make encoding efficient.
The encoder must be able to handle zero length input and return an empty object of the output object type in this situation.
Decodes the object input and returns a tuple (output object, length consumed). For instance, for a text encoding, decoding converts a bytes object encoded using a particular character set encoding to a string object.
For text encodings and bytes-to-bytes codecs, input must be a bytes object or one which provides the read-only buffer interface – for example, buffer objects and memory mapped files.
The errors argument defines the error handling to apply. It defaults to 'strict' handling.
The method may not store state in the Codec instance. Use StreamReader for codecs which have to keep state in order to make decoding efficient.
The decoder must be able to handle zero length input and return an empty object of the output object type in this situation.
The IncrementalEncoder and IncrementalDecoder classes provide the basic interface for incremental encoding and decoding. Encoding/decoding the input isn’t done with one call to the stateless encoder/decoder function, but with multiple calls to the encode()/decode() method of the incremental encoder/decoder. The incremental encoder/decoder keeps track of the encoding/decoding process during method calls.
The joined output of calls to the encode()/decode() method is the same as if all the single inputs were joined into one, and this input was encoded/decoded with the stateless encoder/decoder.
The IncrementalEncoder class is used for encoding an input in multiple steps. It defines the following methods which every incremental encoder must define in order to be compatible with the Python codec registry.
Constructor for an IncrementalEncoder instance.
All incremental encoders must provide this constructor interface. They are free to add additional keyword arguments, but only the ones defined here are used by the Python codec registry.
The IncrementalEncoder may implement different error handling schemes by providing the errors keyword argument. See Error Handlers for possible values.
The errors argument will be assigned to an attribute of the same name. Assigning to this attribute makes it possible to switch between different error handling strategies during the lifetime of the IncrementalEncoder object.
Encodes object (taking the current state of the encoder into account) and returns the resulting encoded object. If this is the last call to encode() final must be true (the default is false).
Reset the encoder to the initial state. The output is discarded: call .encode(object, final=True), passing an empty byte or text string if necessary, to reset the encoder and to get the output.
Return the current state of the encoder which must be an integer. The implementation should make sure that 0 is the most common state. (States that are more complicated than integers can be converted into an integer by marshaling/pickling the state and encoding the bytes of the resulting string into an integer.)
Set the state of the encoder to state. state must be an encoder state returned by getstate().
The IncrementalDecoder class is used for decoding an input in multiple steps. It defines the following methods which every incremental decoder must define in order to be compatible with the Python codec registry.
Constructor for an IncrementalDecoder instance.
All incremental decoders must provide this constructor interface. They are free to add additional keyword arguments, but only the ones defined here are used by the Python codec registry.
The IncrementalDecoder may implement different error handling schemes by providing the errors keyword argument. See Error Handlers for possible values.
The errors argument will be assigned to an attribute of the same name. Assigning to this attribute makes it possible to switch between different error handling strategies during the lifetime of the IncrementalDecoder object.
Decodes object (taking the current state of the decoder into account) and returns the resulting decoded object. If this is the last call to decode() final must be true (the default is false). If final is true the decoder must decode the input completely and must flush all buffers. If this isn’t possible (e.g. because of incomplete byte sequences at the end of the input) it must initiate error handling just like in the stateless case (which might raise an exception).
Reset the decoder to the initial state.
Return the current state of the decoder. This must be a tuple with two items, the first must be the buffer containing the still undecoded input. The second must be an integer and can be additional state info. (The implementation should make sure that 0 is the most common additional state info.) If this additional state info is 0 it must be possible to set the decoder to the state which has no input buffered and 0 as the additional state info, so that feeding the previously buffered input to the decoder returns it to the previous state without producing any output. (Additional state info that is more complicated than integers can be converted into an integer by marshaling/pickling the info and encoding the bytes of the resulting string into an integer.)
Set the state of the decoder to state. state must be a decoder state returned by getstate().
The StreamWriter and StreamReader classes provide generic working interfaces which can be used to implement new encoding submodules very easily. See encodings.utf_8 for an example of how this is done.
The StreamWriter class is a subclass of Codec and defines the following methods which every stream writer must define in order to be compatible with the Python codec registry.
Constructor for a StreamWriter instance.
All stream writers must provide this constructor interface. They are free to add additional keyword arguments, but only the ones defined here are used by the Python codec registry.
The stream argument must be a file-like object open for writing text or binary data, as appropriate for the specific codec.
The StreamWriter may implement different error handling schemes by providing the errors keyword argument. See Error Handlers for the standard error handlers the underlying stream codec may support.
The errors argument will be assigned to an attribute of the same name. Assigning to this attribute makes it possible to switch between different error handling strategies during the lifetime of the StreamWriter object.
Writes the object’s contents encoded to the stream.
Writes the concatenated list of strings to the stream (possibly by reusing the write() method). The standard bytes-to-bytes codecs do not support this method.
Resets the codec buffers used for keeping internal state.
Calling this method should ensure that the data on the output is put into a clean state that allows appending of new fresh data without having to rescan the whole stream to recover state.
In addition to the above methods, the StreamWriter must also inherit all other methods and attributes from the underlying stream.
The StreamReader class is a subclass of Codec and defines the following methods which every stream reader must define in order to be compatible with the Python codec registry.
Constructor for a StreamReader instance.
All stream readers must provide this constructor interface. They are free to add additional keyword arguments, but only the ones defined here are used by the Python codec registry.
The stream argument must be a file-like object open for reading text or binary data, as appropriate for the specific codec.
The StreamReader may implement different error handling schemes by providing the errors keyword argument. See Error Handlers for the standard error handlers the underlying stream codec may support.
The errors argument will be assigned to an attribute of the same name. Assigning to this attribute makes it possible to switch between different error handling strategies during the lifetime of the StreamReader object.
The set of allowed values for the errors argument can be extended with register_error().
Decodes data from the stream and returns the resulting object.
The chars argument indicates the number of decoded code points or bytes to return. The read() method will never return more data than requested, but it might return less, if there is not enough available.
The size argument indicates the approximate maximum number of encoded bytes or code points to read for decoding. The decoder can modify this setting as appropriate. The default value -1 indicates to read and decode as much as possible. This parameter is intended to prevent having to decode huge files in one step.
The firstline flag indicates that it would be sufficient to only return the first line, if there are decoding errors on later lines.
The method should use a greedy read strategy meaning that it should read as much data as is allowed within the definition of the encoding and the given size, e.g. if optional encoding endings or state markers are available on the stream, these should be read too.
Read one line from the input stream and return the decoded data.
size, if given, is passed as size argument to the stream’s read() method.
If keepends is false line-endings will be stripped from the lines returned.
Read all lines available on the input stream and return them as a list of lines.
Line-endings are implemented using the codec’s decode() method and are included in the list entries if keepends is true.
sizehint, if given, is passed as the size argument to the stream’s read() method.
Resets the codec buffers used for keeping internal state.
Note that no stream repositioning should take place. This method is primarily intended to be able to recover from decoding errors.
In addition to the above methods, the StreamReader must also inherit all other methods and attributes from the underlying stream.
The StreamReaderWriter is a convenience class that allows wrapping streams which work in both read and write modes.
The design is such that one can use the factory functions returned by the lookup() function to construct the instance.
Creates a StreamReaderWriter instance. stream must be a file-like object. Reader and Writer must be factory functions or classes providing the StreamReader and StreamWriter interface resp. Error handling is done in the same way as defined for the stream readers and writers.
StreamReaderWriter instances define the combined interfaces of StreamReader and StreamWriter classes. They inherit all other methods and attributes from the underlying stream.
The StreamRecoder translates data from one encoding to another, which is sometimes useful when dealing with different encoding environments.
The design is such that one can use the factory functions returned by the lookup() function to construct the instance.
Creates a StreamRecoder instance which implements a two-way conversion: encode and decode work on the frontend — the data visible to code calling read() and write(), while Reader and Writer work on the backend — the data in stream.
You can use these objects to do transparent transcodings, e.g., from Latin-1 to UTF-8 and back.
The stream argument must be a file-like object.
The encode and decode arguments must adhere to the Codec interface. Reader and Writer must be factory functions or classes providing objects of the StreamReader and StreamWriter interface respectively.
Error handling is done in the same way as defined for the stream readers and writers.
StreamRecoder instances define the combined interfaces of StreamReader and StreamWriter classes. They inherit all other methods and attributes from the underlying stream.
Strings are stored internally as sequences of code points in range 0x0–0x10FFFF. (See PEP 393 for more details about the implementation.) Once a string object is used outside of CPU and memory, endianness and how these arrays are stored as bytes become an issue. As with other codecs, serialising a string into a sequence of bytes is known as encoding, and recreating the string from the sequence of bytes is known as decoding. There are a variety of different text serialisation codecs, which are collectivity referred to as text encodings.
The simplest text encoding (called 'latin-1' or 'iso-8859-1') maps the code points 0–255 to the bytes 0x0–0xff, which means that a string object that contains code points above U+00FF can’t be encoded with this codec. Doing so will raise a UnicodeEncodeError that looks like the following (although the details of the error message may differ): UnicodeEncodeError: 'latin-1' codec can't encode character '\u1234' in
position 3: ordinal not in range(256).
There’s another group of encodings (the so called charmap encodings) that choose a different subset of all Unicode code points and how these code points are mapped to the bytes 0x0–0xff. To see how this is done simply open e.g. encodings/cp1252.py (which is an encoding that is used primarily on Windows). There’s a string constant with 256 characters that shows you which character is mapped to which byte value.
All of these encodings can only encode 256 of the 1114112 code points defined in Unicode. A simple and straightforward way that can store each Unicode code point, is to store each code point as four consecutive bytes. There are two possibilities: store the bytes in big endian or in little endian order. These two encodings are called UTF-32-BE and UTF-32-LE respectively. Their disadvantage is that if e.g. you use UTF-32-BE on a little endian machine you will always have to swap bytes on encoding and decoding. UTF-32 avoids this problem: bytes will always be in natural endianness. When these bytes are read by a CPU with a different endianness, then bytes have to be swapped though. To be able to detect the endianness of a UTF-16 or UTF-32 byte sequence, there’s the so called BOM (“Byte Order Mark”). This is the Unicode character U+FEFF. This character can be prepended to every UTF-16 or UTF-32 byte sequence. The byte swapped version of this character (0xFFFE) is an illegal character that may not appear in a Unicode text. So when the first character in an UTF-16 or UTF-32 byte sequence appears to be a U+FFFE the bytes have to be swapped on decoding. Unfortunately the character U+FEFF had a second purpose as a ZERO WIDTH NO-BREAK SPACE: a character that has no width and doesn’t allow a word to be split. It can e.g. be used to give hints to a ligature algorithm. With Unicode 4.0 using U+FEFF as a ZERO WIDTH NO-BREAK SPACE has been deprecated (with U+2060 (WORD JOINER) assuming this role). Nevertheless Unicode software still must be able to handle U+FEFF in both roles: as a BOM it’s a device to determine the storage layout of the encoded bytes, and vanishes once the byte sequence has been decoded into a string; as a ZERO WIDTH
NO-BREAK SPACE it’s a normal character that will be decoded like any other.
There’s another encoding that is able to encoding the full range of Unicode characters: UTF-8. UTF-8 is an 8-bit encoding, which means there are no issues with byte order in UTF-8. Each byte in a UTF-8 byte sequence consists of two parts: marker bits (the most significant bits) and payload bits. The marker bits are a sequence of zero to four 1 bits followed by a 0 bit. Unicode characters are encoded like this (with x being payload bits, which when concatenated give the Unicode character):
Range
Encoding
U-00000000 … U-0000007F
0xxxxxxx
U-00000080 … U-000007FF
110xxxxx 10xxxxxx
U-00000800 … U-0000FFFF
1110xxxx 10xxxxxx 10xxxxxx
U-00010000 … U-0010FFFF
11110xxx 10xxxxxx 10xxxxxx 10xxxxxx
The least significant bit of the Unicode character is the rightmost x bit.
As UTF-8 is an 8-bit encoding no BOM is required and any U+FEFF character in the decoded string (even if it’s the first character) is treated as a ZERO
WIDTH NO-BREAK SPACE.
Without external information it’s impossible to reliably determine which encoding was used for encoding a string. Each charmap encoding can decode any random byte sequence. However that’s not possible with UTF-8, as UTF-8 byte sequences have a structure that doesn’t allow arbitrary byte sequences. To increase the reliability with which a UTF-8 encoding can be detected, Microsoft invented a variant of UTF-8 (that Python 2.5 calls "utf-8-sig") for its Notepad program: Before any of the Unicode characters is written to the file, a UTF-8 encoded BOM (which looks like this as a byte sequence: 0xef, 0xbb, 0xbf) is written. As it’s rather improbable that any charmap encoded file starts with these byte values (which would e.g. map to
in iso-8859-1), this increases the probability that a utf-8-sig encoding can be correctly guessed from the byte sequence. So here the BOM is not used to be able to determine the byte order used for generating the byte sequence, but as a signature that helps in guessing the encoding. On encoding the utf-8-sig codec will write 0xef, 0xbb, 0xbf as the first three bytes to the file. On decoding utf-8-sig will skip those three bytes if they appear as the first three bytes in the file. In UTF-8, the use of the BOM is discouraged and should generally be avoided.
Python comes with a number of codecs built-in, either implemented as C functions or with dictionaries as mapping tables. The following table lists the codecs by name, together with a few common aliases, and the languages for which the encoding is likely used. Neither the list of aliases nor the list of languages is meant to be exhaustive. Notice that spelling alternatives that only differ in case or use a hyphen instead of an underscore are also valid aliases; therefore, e.g. 'utf-8' is a valid alias for the 'utf_8' codec.
CPython implementation detail: Some common encodings can bypass the codecs lookup machinery to improve performance. These optimization opportunities are only recognized by CPython for a limited set of (case insensitive) aliases: utf-8, utf8, latin-1, latin1, iso-8859-1, iso8859-1, mbcs (Windows only), ascii, us-ascii, utf-16, utf16, utf-32, utf32, and the same using underscores instead of dashes. Using alternative aliases for these encodings may result in slower execution.
Changed in version 3.6: Optimization opportunity recognized for us-ascii.
Many of the character sets support the same languages. They vary in individual characters (e.g. whether the EURO SIGN is supported or not), and in the assignment of characters to code positions. For the European languages in particular, the following variants typically exist:
Codec
Aliases
Languages
ascii
646, us-ascii
English
big5
big5-tw, csbig5
Traditional Chinese
big5hkscs
big5-hkscs, hkscs
Traditional Chinese
cp037
IBM037, IBM039
English
cp273
273, IBM273, csIBM273
German
New in version 3.4.
cp424
EBCDIC-CP-HE, IBM424
Hebrew
cp437
437, IBM437
English
cp500
EBCDIC-CP-BE, EBCDIC-CP-CH, IBM500
Western Europe
cp720
Arabic
cp737
Greek
cp775
IBM775
Baltic languages
cp850
850, IBM850
Western Europe
cp852
852, IBM852
Central and Eastern Europe
cp855
855, IBM855
Bulgarian, Byelorussian, Macedonian, Russian, Serbian
cp856
Hebrew
cp857
857, IBM857
Turkish
cp858
858, IBM858
Western Europe
cp860
860, IBM860
Portuguese
cp861
861, CP-IS, IBM861
Icelandic
cp862
862, IBM862
Hebrew
cp863
863, IBM863
Canadian
cp864
IBM864
Arabic
cp865
865, IBM865
Danish, Norwegian
cp866
866, IBM866
Russian
cp869
869, CP-GR, IBM869
Greek
cp874
Thai
cp875
Greek
cp932
932, ms932, mskanji, ms-kanji
Japanese
cp949
949, ms949, uhc
Korean
cp950
950, ms950
Traditional Chinese
cp1006
Urdu
cp1026
ibm1026
Turkish
cp1125
1125, ibm1125, cp866u, ruscii
Ukrainian
New in version 3.4.
cp1140
ibm1140
Western Europe
cp1250
windows-1250
Central and Eastern Europe
cp1251
windows-1251
Bulgarian, Byelorussian, Macedonian, Russian, Serbian
cp1252
windows-1252
Western Europe
cp1253
windows-1253
Greek
cp1254
windows-1254
Turkish
cp1255
windows-1255
Hebrew
cp1256
windows-1256
Arabic
cp1257
windows-1257
Baltic languages
cp1258
windows-1258
Vietnamese
euc_jp
eucjp, ujis, u-jis
Japanese
euc_jis_2004
jisx0213, eucjis2004
Japanese
euc_jisx0213
eucjisx0213
Japanese
euc_kr
euckr, korean, ksc5601, ks_c-5601, ks_c-5601-1987, ksx1001, ks_x-1001
Korean
gb2312
chinese, csiso58gb231280, euc-cn, euccn, eucgb2312-cn, gb2312-1980, gb2312-80, iso-ir-58
Simplified Chinese
gbk
936, cp936, ms936
Unified Chinese
gb18030
gb18030-2000
Unified Chinese
hz
hzgb, hz-gb, hz-gb-2312
Simplified Chinese
iso2022_jp
csiso2022jp, iso2022jp, iso-2022-jp
Japanese
iso2022_jp_1
iso2022jp-1, iso-2022-jp-1
Japanese
iso2022_jp_2
iso2022jp-2, iso-2022-jp-2
Japanese, Korean, Simplified Chinese, Western Europe, Greek
iso2022_jp_2004
iso2022jp-2004, iso-2022-jp-2004
Japanese
iso2022_jp_3
iso2022jp-3, iso-2022-jp-3
Japanese
iso2022_jp_ext
iso2022jp-ext, iso-2022-jp-ext
Japanese
iso2022_kr
csiso2022kr, iso2022kr, iso-2022-kr
Korean
latin_1
iso-8859-1, iso8859-1, 8859, cp819, latin, latin1, L1
Western Europe
iso8859_2
iso-8859-2, latin2, L2
Central and Eastern Europe
iso8859_3
iso-8859-3, latin3, L3
Esperanto, Maltese
iso8859_4
iso-8859-4, latin4, L4
Baltic languages
iso8859_5
iso-8859-5, cyrillic
Bulgarian, Byelorussian, Macedonian, Russian, Serbian
iso8859_6
iso-8859-6, arabic
Arabic
iso8859_7
iso-8859-7, greek, greek8
Greek
iso8859_8
iso-8859-8, hebrew
Hebrew
iso8859_9
iso-8859-9, latin5, L5
Turkish
iso8859_10
iso-8859-10, latin6, L6
Nordic languages
iso8859_11
iso-8859-11, thai
Thai languages
iso8859_13
iso-8859-13, latin7, L7
Baltic languages
iso8859_14
iso-8859-14, latin8, L8
Celtic languages
iso8859_15
iso-8859-15, latin9, L9
Western Europe
iso8859_16
iso-8859-16, latin10, L10
South-Eastern Europe
johab
cp1361, ms1361
Korean
koi8_r
Russian
koi8_t
Tajik
New in version 3.5.
koi8_u
Ukrainian
kz1048
kz_1048, strk1048_2002, rk1048
Kazakh
New in version 3.5.
mac_cyrillic
maccyrillic
Bulgarian, Byelorussian, Macedonian, Russian, Serbian
mac_greek
macgreek
Greek
mac_iceland
maciceland
Icelandic
mac_latin2
maclatin2, maccentraleurope, mac_centeuro
Central and Eastern Europe
mac_roman
macroman, macintosh
Western Europe
mac_turkish
macturkish
Turkish
ptcp154
csptcp154, pt154, cp154, cyrillic-asian
Kazakh
shift_jis
csshiftjis, shiftjis, sjis, s_jis
Japanese
shift_jis_2004
shiftjis2004, sjis_2004, sjis2004
Japanese
shift_jisx0213
shiftjisx0213, sjisx0213, s_jisx0213
Japanese
utf_32
U32, utf32
all languages
utf_32_be
UTF-32BE
all languages
utf_32_le
UTF-32LE
all languages
utf_16
U16, utf16
all languages
utf_16_be
UTF-16BE
all languages
utf_16_le
UTF-16LE
all languages
utf_7
U7, unicode-1-1-utf-7
all languages
utf_8
U8, UTF, utf8, cp65001
all languages
utf_8_sig
all languages
Changed in version 3.4: The utf-16* and utf-32* encoders no longer allow surrogate code points (U+D800–U+DFFF) to be encoded. The utf-32* decoders no longer decode byte sequences that correspond to surrogate code points.
Changed in version 3.8: cp65001 is now an alias to utf_8.
A number of predefined codecs are specific to Python, so their codec names have no meaning outside Python. These are listed in the tables below based on the expected input and output types (note that while text encodings are the most common use case for codecs, the underlying codec infrastructure supports arbitrary data transforms rather than just text encodings). For asymmetric codecs, the stated meaning describes the encoding direction.
The following codecs provide str to bytes encoding and bytes-like object to str decoding, similar to the Unicode text encodings.
Codec
Aliases
Meaning
idna
Implement RFC 3490, see also encodings.idna. Only errors='strict' is supported.
mbcs
ansi, dbcs
Windows only: Encode the operand according to the ANSI codepage (CP_ACP).
oem
Windows only: Encode the operand according to the OEM codepage (CP_OEMCP).
New in version 3.6.
palmos
Encoding of PalmOS 3.5.
punycode
Implement RFC 3492. Stateful codecs are not supported.
raw_unicode_escape
Latin-1 encoding with \uXXXX and \UXXXXXXXX for other code points. Existing backslashes are not escaped in any way. It is used in the Python pickle protocol.
undefined
Raise an exception for all conversions, even empty strings. The error handler is ignored.
unicode_escape
Encoding suitable as the contents of a Unicode literal in ASCII-encoded Python source code, except that quotes are not escaped. Decode from Latin-1 source code. Beware that Python source code actually uses UTF-8 by default.
Changed in version 3.8: “unicode_internal” codec is removed.
The following codecs provide binary transforms: bytes-like object to bytes mappings. They are not supported by bytes.decode() (which only produces str output).
Codec
Aliases
Meaning
Encoder / decoder
base64_codec 1
base64, base_64
Convert the operand to multiline MIME base64 (the result always includes a trailing '\n').
Changed in version 3.4: accepts any bytes-like object as input for encoding and decoding
base64.encodebytes() / base64.decodebytes()
bz2_codec
bz2
Compress the operand using bz2.
bz2.compress() / bz2.decompress()
hex_codec
hex
Convert the operand to hexadecimal representation, with two digits per byte.
binascii.b2a_hex() / binascii.a2b_hex()
quopri_codec
quopri, quotedprintable, quoted_printable
Convert the operand to MIME quoted printable.
quopri.encode() with quotetabs=True / quopri.decode()
uu_codec
uu
Convert the operand using uuencode.
uu.encode() / uu.decode()
zlib_codec
zip, zlib
Compress the operand using gzip.
zlib.compress() / zlib.decompress()
In addition to bytes-like objects, 'base64_codec' also accepts ASCII-only instances of str for decoding
New in version 3.2: Restoration of the binary transforms.
Changed in version 3.4: Restoration of the aliases for the binary transforms.
The following codec provides a text transform: a str to str mapping. It is not supported by str.encode() (which only produces bytes output).
Codec
Aliases
Meaning
rot_13
rot13
Return the Caesar-cypher encryption of the operand.
New in version 3.2: Restoration of the rot_13 text transform.
Changed in version 3.4: Restoration of the rot13 alias.
This module implements RFC 3490 (Internationalized Domain Names in Applications) and RFC 3492 (Nameprep: A Stringprep Profile for Internationalized Domain Names (IDN)). It builds upon the punycode encoding and stringprep.
If you need the IDNA 2008 standard from RFC 5891 and RFC 5895, use the third-party idna module <https://pypi.org/project/idna/>_.
These RFCs together define a protocol to support non-ASCII characters in domain names. A domain name containing non-ASCII characters (such as www.Alliancefrançaise.nu) is converted into an ASCII-compatible encoding (ACE, such as www.xn--alliancefranaise-npb.nu). The ACE form of the domain name is then used in all places where arbitrary characters are not allowed by the protocol, such as DNS queries, HTTP Host fields, and so on. This conversion is carried out in the application; if possible invisible to the user: The application should transparently convert Unicode domain labels to IDNA on the wire, and convert back ACE labels to Unicode before presenting them to the user.
Python supports this conversion in several ways: the idna codec performs conversion between Unicode and ACE, separating an input string into labels based on the separator characters defined in section 3.1 of RFC 3490 and converting each label to ACE as required, and conversely separating an input byte string into labels based on the . separator and converting any ACE labels found into unicode. Furthermore, the socket module transparently converts Unicode host names to ACE, so that applications need not be concerned about converting host names themselves when they pass them to the socket module. On top of that, modules that have host names as function parameters, such as http.client and ftplib, accept Unicode host names (http.client then also transparently sends an IDNA hostname in the Host field if it sends that field at all).
When receiving host names from the wire (such as in reverse name lookup), no automatic conversion to Unicode is performed: applications wishing to present such host names to the user should decode them to Unicode.
The module encodings.idna also implements the nameprep procedure, which performs certain normalizations on host names, to achieve case-insensitivity of international domain names, and to unify similar characters. The nameprep functions can be used directly if desired.
Return the nameprepped version of label. The implementation currently assumes query strings, so AllowUnassigned is true.
Convert a label to ASCII, as specified in RFC 3490. UseSTD3ASCIIRules is assumed to be false.
Convert a label to Unicode, as specified in RFC 3490.
This module implements the ANSI codepage (CP_ACP).
Availability: Windows only.
Changed in version 3.3: Support any error handler.
Changed in version 3.2: Before 3.2, the errors argument was ignored; 'replace' was always used to encode, and 'ignore' to decode.
This module implements a variant of the UTF-8 codec. On encoding, a UTF-8 encoded BOM will be prepended to the UTF-8 encoded bytes. For the stateful encoder this is only done once (on the first write to the byte stream). On decoding, an optional UTF-8 encoded BOM at the start of the data will be skipped.


Implements the 'backslashreplace' error handling (for text encodings only): malformed data is replaced by a backslashed escape sequence.


These constants define various byte sequences, being Unicode byte order marks (BOMs) for several encodings. They are used in UTF-16 and UTF-32 data streams to indicate the byte order used, and in UTF-8 as a Unicode signature. BOM_UTF16 is either BOM_UTF16_BE or BOM_UTF16_LE depending on the platform’s native byte order, BOM is an alias for BOM_UTF16, BOM_LE for BOM_UTF16_LE and BOM_BE for BOM_UTF16_BE. The others represent the BOM in UTF-8 and UTF-32 encodings.


Decodes the object input and returns a tuple (output object, length consumed). For instance, for a text encoding, decoding converts a bytes object encoded using a particular character set encoding to a string object.
For text encodings and bytes-to-bytes codecs, input must be a bytes object or one which provides the read-only buffer interface – for example, buffer objects and memory mapped files.
The errors argument defines the error handling to apply. It defaults to 'strict' handling.
The method may not store state in the Codec instance. Use StreamReader for codecs which have to keep state in order to make decoding efficient.
The decoder must be able to handle zero length input and return an empty object of the output object type in this situation.


Encodes the object input and returns a tuple (output object, length consumed). For instance, text encoding converts a string object to a bytes object using a particular character set encoding (e.g., cp1252 or iso-8859-1).
The errors argument defines the error handling to apply. It defaults to 'strict' handling.
The method may not store state in the Codec instance. Use StreamWriter for codecs which have to keep state in order to make encoding efficient.
The encoder must be able to handle zero length input and return an empty object of the output object type in this situation.


Codec details when looking up the codec registry. The constructor arguments are stored in attributes of the same name:
The name of the encoding.
The stateless encoding and decoding functions. These must be functions or methods which have the same interface as the encode() and decode() methods of Codec instances (see Codec Interface). The functions or methods are expected to work in a stateless mode.
Incremental encoder and decoder classes or factory functions. These have to provide the interface defined by the base classes IncrementalEncoder and IncrementalDecoder, respectively. Incremental codecs can maintain state.
Stream writer and reader classes or factory functions. These have to provide the interface defined by the base classes StreamWriter and StreamReader, respectively. Stream codecs can maintain state.


The stateless encoding and decoding functions. These must be functions or methods which have the same interface as the encode() and decode() methods of Codec instances (see Codec Interface). The functions or methods are expected to work in a stateless mode.


Incremental encoder and decoder classes or factory functions. These have to provide the interface defined by the base classes IncrementalEncoder and IncrementalDecoder, respectively. Incremental codecs can maintain state.


Stream writer and reader classes or factory functions. These have to provide the interface defined by the base classes StreamWriter and StreamReader, respectively. Stream codecs can maintain state.


Decodes obj using the codec registered for encoding.
Errors may be given to set the desired error handling scheme. The default error handler is 'strict' meaning that decoding errors raise ValueError (or a more codec specific subclass, such as UnicodeDecodeError). Refer to Codec Base Classes for more information on codec error handling.


Encodes obj using the codec registered for encoding.
Errors may be given to set the desired error handling scheme. The default error handler is 'strict' meaning that encoding errors raise ValueError (or a more codec specific subclass, such as UnicodeEncodeError). Refer to Codec Base Classes for more information on codec error handling.


Return a StreamRecoder instance, a wrapped version of file which provides transparent transcoding. The original file is closed when the wrapped version is closed.
Data written to the wrapped file is decoded according to the given data_encoding and then written to the original file as bytes using file_encoding. Bytes read from the original file are decoded according to file_encoding, and the result is encoded using data_encoding.
If file_encoding is not given, it defaults to data_encoding.
errors may be given to define the error handling. It defaults to 'strict', which causes ValueError to be raised in case an encoding error occurs.


Look up the codec for the given encoding and return its decoder function.
Raises a LookupError in case the encoding cannot be found.


Look up the codec for the given encoding and return its encoder function.
Raises a LookupError in case the encoding cannot be found.


Look up the codec for the given encoding and return its incremental decoder class or factory function.
Raises a LookupError in case the encoding cannot be found or the codec doesn’t support an incremental decoder.


Look up the codec for the given encoding and return its incremental encoder class or factory function.
Raises a LookupError in case the encoding cannot be found or the codec doesn’t support an incremental encoder.


Look up the codec for the given encoding and return its StreamReader class or factory function.
Raises a LookupError in case the encoding cannot be found.


Look up the codec for the given encoding and return its StreamWriter class or factory function.
Raises a LookupError in case the encoding cannot be found.


Implements the 'ignore' error handling: malformed data is ignored and encoding or decoding is continued without further notice.


Constructor for an IncrementalDecoder instance.
All incremental decoders must provide this constructor interface. They are free to add additional keyword arguments, but only the ones defined here are used by the Python codec registry.
The IncrementalDecoder may implement different error handling schemes by providing the errors keyword argument. See Error Handlers for possible values.
The errors argument will be assigned to an attribute of the same name. Assigning to this attribute makes it possible to switch between different error handling strategies during the lifetime of the IncrementalDecoder object.
Decodes object (taking the current state of the decoder into account) and returns the resulting decoded object. If this is the last call to decode() final must be true (the default is false). If final is true the decoder must decode the input completely and must flush all buffers. If this isn’t possible (e.g. because of incomplete byte sequences at the end of the input) it must initiate error handling just like in the stateless case (which might raise an exception).
Reset the decoder to the initial state.
Return the current state of the decoder. This must be a tuple with two items, the first must be the buffer containing the still undecoded input. The second must be an integer and can be additional state info. (The implementation should make sure that 0 is the most common additional state info.) If this additional state info is 0 it must be possible to set the decoder to the state which has no input buffered and 0 as the additional state info, so that feeding the previously buffered input to the decoder returns it to the previous state without producing any output. (Additional state info that is more complicated than integers can be converted into an integer by marshaling/pickling the info and encoding the bytes of the resulting string into an integer.)
Set the state of the decoder to state. state must be a decoder state returned by getstate().


Decodes object (taking the current state of the decoder into account) and returns the resulting decoded object. If this is the last call to decode() final must be true (the default is false). If final is true the decoder must decode the input completely and must flush all buffers. If this isn’t possible (e.g. because of incomplete byte sequences at the end of the input) it must initiate error handling just like in the stateless case (which might raise an exception).


Return the current state of the decoder. This must be a tuple with two items, the first must be the buffer containing the still undecoded input. The second must be an integer and can be additional state info. (The implementation should make sure that 0 is the most common additional state info.) If this additional state info is 0 it must be possible to set the decoder to the state which has no input buffered and 0 as the additional state info, so that feeding the previously buffered input to the decoder returns it to the previous state without producing any output. (Additional state info that is more complicated than integers can be converted into an integer by marshaling/pickling the info and encoding the bytes of the resulting string into an integer.)


Set the state of the decoder to state. state must be a decoder state returned by getstate().


Constructor for an IncrementalEncoder instance.
All incremental encoders must provide this constructor interface. They are free to add additional keyword arguments, but only the ones defined here are used by the Python codec registry.
The IncrementalEncoder may implement different error handling schemes by providing the errors keyword argument. See Error Handlers for possible values.
The errors argument will be assigned to an attribute of the same name. Assigning to this attribute makes it possible to switch between different error handling strategies during the lifetime of the IncrementalEncoder object.
Encodes object (taking the current state of the encoder into account) and returns the resulting encoded object. If this is the last call to encode() final must be true (the default is false).
Reset the encoder to the initial state. The output is discarded: call .encode(object, final=True), passing an empty byte or text string if necessary, to reset the encoder and to get the output.
Return the current state of the encoder which must be an integer. The implementation should make sure that 0 is the most common state. (States that are more complicated than integers can be converted into an integer by marshaling/pickling the state and encoding the bytes of the resulting string into an integer.)
Set the state of the encoder to state. state must be an encoder state returned by getstate().


Encodes object (taking the current state of the encoder into account) and returns the resulting encoded object. If this is the last call to encode() final must be true (the default is false).


Return the current state of the encoder which must be an integer. The implementation should make sure that 0 is the most common state. (States that are more complicated than integers can be converted into an integer by marshaling/pickling the state and encoding the bytes of the resulting string into an integer.)


Reset the encoder to the initial state. The output is discarded: call .encode(object, final=True), passing an empty byte or text string if necessary, to reset the encoder and to get the output.


Set the state of the encoder to state. state must be an encoder state returned by getstate().


Uses an incremental decoder to iteratively decode the input provided by iterator. This function is a generator. The errors argument (as well as any other keyword argument) is passed through to the incremental decoder.
This function requires that the codec accept bytes objects to decode. Therefore it does not support text-to-text encoders such as rot_13, although rot_13 may be used equivalently with iterencode().


Uses an incremental encoder to iteratively encode the input provided by iterator. This function is a generator. The errors argument (as well as any other keyword argument) is passed through to the incremental encoder.
This function requires that the codec accept text str objects to encode. Therefore it does not support bytes-to-bytes encoders such as base64_codec.


Looks up the codec info in the Python codec registry and returns a CodecInfo object as defined below.
Encodings are first looked up in the registry’s cache. If not found, the list of registered search functions is scanned. If no CodecInfo object is found, a LookupError is raised. Otherwise, the CodecInfo object is stored in the cache and returned to the caller.


Return the error handler previously registered under the name name.
Raises a LookupError in case the handler cannot be found.


Implements the 'namereplace' error handling (for encoding with text encodings only): the unencodable character is replaced by a \N{...} escape sequence.
New in version 3.5.


Open an encoded file using the given mode and return an instance of StreamReaderWriter, providing transparent encoding/decoding. The default file mode is 'r', meaning to open the file in read mode.
Note
Underlying encoded files are always opened in binary mode. No automatic conversion of '\n' is done on reading and writing. The mode argument may be any binary mode acceptable to the built-in open() function; the 'b' is automatically added.
encoding specifies the encoding which is to be used for the file. Any encoding that encodes to and decodes from bytes is allowed, and the data types supported by the file methods depend on the codec used.
errors may be given to define the error handling. It defaults to 'strict' which causes a ValueError to be raised in case an encoding error occurs.
buffering has the same meaning as for the built-in open() function. It defaults to -1 which means that the default buffer size will be used.


Register a codec search function. Search functions are expected to take one argument, being the encoding name in all lower case letters with hyphens and spaces converted to underscores, and return a CodecInfo object. In case a search function cannot find a given encoding, it should return None.
Changed in version 3.9: Hyphens and spaces are converted to underscore.
Note
Search function registration is not currently reversible, which may cause problems in some cases, such as unit testing or module reloading.


Register the error handling function error_handler under the name name. The error_handler argument will be called during encoding and decoding in case of an error, when name is specified as the errors parameter.
For encoding, error_handler will be called with a UnicodeEncodeError instance, which contains information about the location of the error. The error handler must either raise this or a different exception, or return a tuple with a replacement for the unencodable part of the input and a position where encoding should continue. The replacement may be either str or bytes. If the replacement is bytes, the encoder will simply copy them into the output buffer. If the replacement is a string, the encoder will encode the replacement. Encoding continues on original input at the specified position. Negative position values will be treated as being relative to the end of the input string. If the resulting position is out of bound an IndexError will be raised.
Decoding and translating works similarly, except UnicodeDecodeError or UnicodeTranslateError will be passed to the handler and that the replacement from the error handler will be put into the output directly.


Implements the 'replace' error handling (for text encodings only): substitutes '?' for encoding errors (to be encoded by the codec), and '\ufffd' (the Unicode replacement character) for decoding errors.


Constructor for a StreamReader instance.
All stream readers must provide this constructor interface. They are free to add additional keyword arguments, but only the ones defined here are used by the Python codec registry.
The stream argument must be a file-like object open for reading text or binary data, as appropriate for the specific codec.
The StreamReader may implement different error handling schemes by providing the errors keyword argument. See Error Handlers for the standard error handlers the underlying stream codec may support.
The errors argument will be assigned to an attribute of the same name. Assigning to this attribute makes it possible to switch between different error handling strategies during the lifetime of the StreamReader object.
The set of allowed values for the errors argument can be extended with register_error().
Decodes data from the stream and returns the resulting object.
The chars argument indicates the number of decoded code points or bytes to return. The read() method will never return more data than requested, but it might return less, if there is not enough available.
The size argument indicates the approximate maximum number of encoded bytes or code points to read for decoding. The decoder can modify this setting as appropriate. The default value -1 indicates to read and decode as much as possible. This parameter is intended to prevent having to decode huge files in one step.
The firstline flag indicates that it would be sufficient to only return the first line, if there are decoding errors on later lines.
The method should use a greedy read strategy meaning that it should read as much data as is allowed within the definition of the encoding and the given size, e.g. if optional encoding endings or state markers are available on the stream, these should be read too.
Read one line from the input stream and return the decoded data.
size, if given, is passed as size argument to the stream’s read() method.
If keepends is false line-endings will be stripped from the lines returned.
Read all lines available on the input stream and return them as a list of lines.
Line-endings are implemented using the codec’s decode() method and are included in the list entries if keepends is true.
sizehint, if given, is passed as the size argument to the stream’s read() method.
Resets the codec buffers used for keeping internal state.
Note that no stream repositioning should take place. This method is primarily intended to be able to recover from decoding errors.


Decodes data from the stream and returns the resulting object.
The chars argument indicates the number of decoded code points or bytes to return. The read() method will never return more data than requested, but it might return less, if there is not enough available.
The size argument indicates the approximate maximum number of encoded bytes or code points to read for decoding. The decoder can modify this setting as appropriate. The default value -1 indicates to read and decode as much as possible. This parameter is intended to prevent having to decode huge files in one step.
The firstline flag indicates that it would be sufficient to only return the first line, if there are decoding errors on later lines.
The method should use a greedy read strategy meaning that it should read as much data as is allowed within the definition of the encoding and the given size, e.g. if optional encoding endings or state markers are available on the stream, these should be read too.


Read one line from the input stream and return the decoded data.
size, if given, is passed as size argument to the stream’s read() method.
If keepends is false line-endings will be stripped from the lines returned.


Read all lines available on the input stream and return them as a list of lines.
Line-endings are implemented using the codec’s decode() method and are included in the list entries if keepends is true.
sizehint, if given, is passed as the size argument to the stream’s read() method.


Resets the codec buffers used for keeping internal state.
Note that no stream repositioning should take place. This method is primarily intended to be able to recover from decoding errors.


Creates a StreamReaderWriter instance. stream must be a file-like object. Reader and Writer must be factory functions or classes providing the StreamReader and StreamWriter interface resp. Error handling is done in the same way as defined for the stream readers and writers.


Creates a StreamRecoder instance which implements a two-way conversion: encode and decode work on the frontend — the data visible to code calling read() and write(), while Reader and Writer work on the backend — the data in stream.
You can use these objects to do transparent transcodings, e.g., from Latin-1 to UTF-8 and back.
The stream argument must be a file-like object.
The encode and decode arguments must adhere to the Codec interface. Reader and Writer must be factory functions or classes providing objects of the StreamReader and StreamWriter interface respectively.
Error handling is done in the same way as defined for the stream readers and writers.


Constructor for a StreamWriter instance.
All stream writers must provide this constructor interface. They are free to add additional keyword arguments, but only the ones defined here are used by the Python codec registry.
The stream argument must be a file-like object open for writing text or binary data, as appropriate for the specific codec.
The StreamWriter may implement different error handling schemes by providing the errors keyword argument. See Error Handlers for the standard error handlers the underlying stream codec may support.
The errors argument will be assigned to an attribute of the same name. Assigning to this attribute makes it possible to switch between different error handling strategies during the lifetime of the StreamWriter object.
Writes the object’s contents encoded to the stream.
Writes the concatenated list of strings to the stream (possibly by reusing the write() method). The standard bytes-to-bytes codecs do not support this method.
Resets the codec buffers used for keeping internal state.
Calling this method should ensure that the data on the output is put into a clean state that allows appending of new fresh data without having to rescan the whole stream to recover state.


Resets the codec buffers used for keeping internal state.
Calling this method should ensure that the data on the output is put into a clean state that allows appending of new fresh data without having to rescan the whole stream to recover state.


Writes the object’s contents encoded to the stream.


Writes the concatenated list of strings to the stream (possibly by reusing the write() method). The standard bytes-to-bytes codecs do not support this method.


Implements the 'strict' error handling: each encoding or decoding error raises a UnicodeError.


Implements the 'xmlcharrefreplace' error handling (for encoding with text encodings only): the unencodable character is replaced by an appropriate XML character reference.


Source code: Lib/codeop.py
The codeop module provides utilities upon which the Python read-eval-print loop can be emulated, as is done in the code module. As a result, you probably don’t want to use the module directly; if you want to include such a loop in your program you probably want to use the code module instead.
There are two parts to this job:
The codeop module provides a way of doing each of these things, and a way of doing them both.
To do just the former:
Tries to compile source, which should be a string of Python code and return a code object if source is valid Python code. In that case, the filename attribute of the code object will be filename, which defaults to '<input>'. Returns None if source is not valid Python code, but is a prefix of valid Python code.
If there is a problem with source, an exception will be raised. SyntaxError is raised if there is invalid Python syntax, and OverflowError or ValueError if there is an invalid literal.
The symbol argument determines whether source is compiled as a statement ('single', the default), as a sequence of statements ('exec') or as an expression ('eval'). Any other value will cause ValueError to be raised.
Note
It is possible (but not likely) that the parser stops parsing with a successful outcome before reaching the end of the source; in this case, trailing symbols may be ignored instead of causing an error. For example, a backslash followed by two newlines may be followed by arbitrary garbage. This will be fixed once the API for the parser is better.
Instances of this class have __call__() methods identical in signature to the built-in function compile(), but with the difference that if the instance compiles program text containing a __future__ statement, the instance ‘remembers’ and compiles all subsequent program texts with the statement in force.
Instances of this class have __call__() methods identical in signature to compile_command(); the difference is that if the instance compiles program text containing a __future__ statement, the instance ‘remembers’ and compiles all subsequent program texts with the statement in force.


Instances of this class have __call__() methods identical in signature to compile_command(); the difference is that if the instance compiles program text containing a __future__ statement, the instance ‘remembers’ and compiles all subsequent program texts with the statement in force.


Instances of this class have __call__() methods identical in signature to the built-in function compile(), but with the difference that if the instance compiles program text containing a __future__ statement, the instance ‘remembers’ and compiles all subsequent program texts with the statement in force.


Tries to compile source, which should be a string of Python code and return a code object if source is valid Python code. In that case, the filename attribute of the code object will be filename, which defaults to '<input>'. Returns None if source is not valid Python code, but is a prefix of valid Python code.
If there is a problem with source, an exception will be raised. SyntaxError is raised if there is invalid Python syntax, and OverflowError or ValueError if there is an invalid literal.
The symbol argument determines whether source is compiled as a statement ('single', the default), as a sequence of statements ('exec') or as an expression ('eval'). Any other value will cause ValueError to be raised.
Note
It is possible (but not likely) that the parser stops parsing with a successful outcome before reaching the end of the source; in this case, trailing symbols may be ignored instead of causing an error. For example, a backslash followed by two newlines may be followed by arbitrary garbage. This will be fixed once the API for the parser is better.


Source code: Lib/collections/__init__.py
This module implements specialized container datatypes providing alternatives to Python’s general purpose built-in containers, dict, list, set, and tuple.
namedtuple()
factory function for creating tuple subclasses with named fields
deque
list-like container with fast appends and pops on either end
ChainMap
dict-like class for creating a single view of multiple mappings
Counter
dict subclass for counting hashable objects
OrderedDict
dict subclass that remembers the order entries were added
defaultdict
dict subclass that calls a factory function to supply missing values
UserDict
wrapper around dictionary objects for easier dict subclassing
UserList
wrapper around list objects for easier list subclassing
UserString
wrapper around string objects for easier string subclassing
Deprecated since version 3.3, will be removed in version 3.10: Moved Collections Abstract Base Classes to the collections.abc module. For backwards compatibility, they continue to be visible in this module through Python 3.9.
New in version 3.3.
A ChainMap class is provided for quickly linking a number of mappings so they can be treated as a single unit. It is often much faster than creating a new dictionary and running multiple update() calls.
The class can be used to simulate nested scopes and is useful in templating.
A ChainMap groups multiple dicts or other mappings together to create a single, updateable view. If no maps are specified, a single empty dictionary is provided so that a new chain always has at least one mapping.
The underlying mappings are stored in a list. That list is public and can be accessed or updated using the maps attribute. There is no other state.
Lookups search the underlying mappings successively until a key is found. In contrast, writes, updates, and deletions only operate on the first mapping.
A ChainMap incorporates the underlying mappings by reference. So, if one of the underlying mappings gets updated, those changes will be reflected in ChainMap.
All of the usual dictionary methods are supported. In addition, there is a maps attribute, a method for creating new subcontexts, and a property for accessing all but the first mapping:
A user updateable list of mappings. The list is ordered from first-searched to last-searched. It is the only stored state and can be modified to change which mappings are searched. The list should always contain at least one mapping.
Returns a new ChainMap containing a new map followed by all of the maps in the current instance. If m is specified, it becomes the new map at the front of the list of mappings; if not specified, an empty dict is used, so that a call to d.new_child() is equivalent to: ChainMap({}, *d.maps). This method is used for creating subcontexts that can be updated without altering values in any of the parent mappings.
Changed in version 3.4: The optional m parameter was added.
Property returning a new ChainMap containing all of the maps in the current instance except the first one. This is useful for skipping the first map in the search. Use cases are similar to those for the nonlocal keyword used in nested scopes. The use cases also parallel those for the built-in super() function. A reference to d.parents is equivalent to: ChainMap(*d.maps[1:]).
Note, the iteration order of a ChainMap() is determined by scanning the mappings last to first:
This gives the same ordering as a series of dict.update() calls starting with the last mapping:
Changed in version 3.9: Added support for | and |= operators, specified in PEP 584.
See also
This section shows various approaches to working with chained maps.
Example of simulating Python’s internal lookup chain:
Example of letting user specified command-line arguments take precedence over environment variables which in turn take precedence over default values:
Example patterns for using the ChainMap class to simulate nested contexts:
The ChainMap class only makes updates (writes and deletions) to the first mapping in the chain while lookups will search the full chain. However, if deep writes and deletions are desired, it is easy to make a subclass that updates keys found deeper in the chain:
A counter tool is provided to support convenient and rapid tallies. For example:
A Counter is a dict subclass for counting hashable objects. It is a collection where elements are stored as dictionary keys and their counts are stored as dictionary values. Counts are allowed to be any integer value including zero or negative counts. The Counter class is similar to bags or multisets in other languages.
Elements are counted from an iterable or initialized from another mapping (or counter):
Counter objects have a dictionary interface except that they return a zero count for missing items instead of raising a KeyError:
Setting a count to zero does not remove an element from a counter. Use del to remove it entirely:
New in version 3.1.
Changed in version 3.7: As a dict subclass, Counter Inherited the capability to remember insertion order. Math operations on Counter objects also preserve order. Results are ordered according to when an element is first encountered in the left operand and then by the order encountered in the right operand.
Counter objects support three methods beyond those available for all dictionaries:
Return an iterator over elements repeating each as many times as its count. Elements are returned in the order first encountered. If an element’s count is less than one, elements() will ignore it.
Return a list of the n most common elements and their counts from the most common to the least. If n is omitted or None, most_common() returns all elements in the counter. Elements with equal counts are ordered in the order first encountered:
Elements are subtracted from an iterable or from another mapping (or counter). Like dict.update() but subtracts counts instead of replacing them. Both inputs and outputs may be zero or negative.
New in version 3.2.
The usual dictionary methods are available for Counter objects except for two which work differently for counters.
This class method is not implemented for Counter objects.
Elements are counted from an iterable or added-in from another mapping (or counter). Like dict.update() but adds counts instead of replacing them. Also, the iterable is expected to be a sequence of elements, not a sequence of (key, value) pairs.
Common patterns for working with Counter objects:
Several mathematical operations are provided for combining Counter objects to produce multisets (counters that have counts greater than zero). Addition and subtraction combine counters by adding or subtracting the counts of corresponding elements. Intersection and union return the minimum and maximum of corresponding counts. Each operation can accept inputs with signed counts, but the output will exclude results with counts of zero or less.
Unary addition and subtraction are shortcuts for adding an empty counter or subtracting from an empty counter.
New in version 3.3: Added support for unary plus, unary minus, and in-place multiset operations.
Note
Counters were primarily designed to work with positive integers to represent running counts; however, care was taken to not unnecessarily preclude use cases needing other types or negative values. To help with those use cases, this section documents the minimum range and type restrictions.
See also
To enumerate all distinct multisets of a given size over a given set of elements, see itertools.combinations_with_replacement():
Returns a new deque object initialized left-to-right (using append()) with data from iterable. If iterable is not specified, the new deque is empty.
Deques are a generalization of stacks and queues (the name is pronounced “deck” and is short for “double-ended queue”). Deques support thread-safe, memory efficient appends and pops from either side of the deque with approximately the same O(1) performance in either direction.
Though list objects support similar operations, they are optimized for fast fixed-length operations and incur O(n) memory movement costs for pop(0) and insert(0, v) operations which change both the size and position of the underlying data representation.
If maxlen is not specified or is None, deques may grow to an arbitrary length. Otherwise, the deque is bounded to the specified maximum length. Once a bounded length deque is full, when new items are added, a corresponding number of items are discarded from the opposite end. Bounded length deques provide functionality similar to the tail filter in Unix. They are also useful for tracking transactions and other pools of data where only the most recent activity is of interest.
Deque objects support the following methods:
Add x to the right side of the deque.
Add x to the left side of the deque.
Remove all elements from the deque leaving it with length 0.
Create a shallow copy of the deque.
New in version 3.5.
Count the number of deque elements equal to x.
New in version 3.2.
Extend the right side of the deque by appending elements from the iterable argument.
Extend the left side of the deque by appending elements from iterable. Note, the series of left appends results in reversing the order of elements in the iterable argument.
Return the position of x in the deque (at or after index start and before index stop). Returns the first match or raises ValueError if not found.
New in version 3.5.
Insert x into the deque at position i.
If the insertion would cause a bounded deque to grow beyond maxlen, an IndexError is raised.
New in version 3.5.
Remove and return an element from the right side of the deque. If no elements are present, raises an IndexError.
Remove and return an element from the left side of the deque. If no elements are present, raises an IndexError.
Remove the first occurrence of value. If not found, raises a ValueError.
Reverse the elements of the deque in-place and then return None.
New in version 3.2.
Rotate the deque n steps to the right. If n is negative, rotate to the left.
When the deque is not empty, rotating one step to the right is equivalent to d.appendleft(d.pop()), and rotating one step to the left is equivalent to d.append(d.popleft()).
Deque objects also provide one read-only attribute:
Maximum size of a deque or None if unbounded.
New in version 3.1.
In addition to the above, deques support iteration, pickling, len(d), reversed(d), copy.copy(d), copy.deepcopy(d), membership testing with the in operator, and subscript references such as d[0] to access the first element. Indexed access is O(1) at both ends but slows to O(n) in the middle. For fast random access, use lists instead.
Starting in version 3.5, deques support __add__(), __mul__(), and __imul__().
Example:
This section shows various approaches to working with deques.
Bounded length deques provide functionality similar to the tail filter in Unix:
Another approach to using deques is to maintain a sequence of recently added elements by appending to the right and popping to the left:
A round-robin scheduler can be implemented with input iterators stored in a deque. Values are yielded from the active iterator in position zero. If that iterator is exhausted, it can be removed with popleft(); otherwise, it can be cycled back to the end with the rotate() method:
The rotate() method provides a way to implement deque slicing and deletion. For example, a pure Python implementation of del d[n] relies on the rotate() method to position elements to be popped:
To implement deque slicing, use a similar approach applying rotate() to bring a target element to the left side of the deque. Remove old entries with popleft(), add new entries with extend(), and then reverse the rotation. With minor variations on that approach, it is easy to implement Forth style stack manipulations such as dup, drop, swap, over, pick, rot, and roll.
Returns a new dictionary-like object. defaultdict is a subclass of the built-in dict class. It overrides one method and adds one writable instance variable. The remaining functionality is the same as for the dict class and is not documented here.
The first argument provides the initial value for the default_factory attribute; it defaults to None. All remaining arguments are treated the same as if they were passed to the dict constructor, including keyword arguments.
defaultdict objects support the following method in addition to the standard dict operations:
If the default_factory attribute is None, this raises a KeyError exception with the key as argument.
If default_factory is not None, it is called without arguments to provide a default value for the given key, this value is inserted in the dictionary for the key, and returned.
If calling default_factory raises an exception this exception is propagated unchanged.
This method is called by the __getitem__() method of the dict class when the requested key is not found; whatever it returns or raises is then returned or raised by __getitem__().
Note that __missing__() is not called for any operations besides __getitem__(). This means that get() will, like normal dictionaries, return None as a default rather than using default_factory.
defaultdict objects support the following instance variable:
This attribute is used by the __missing__() method; it is initialized from the first argument to the constructor, if present, or to None, if absent.
Changed in version 3.9: Added merge (|) and update (|=) operators, specified in PEP 584.
Using list as the default_factory, it is easy to group a sequence of key-value pairs into a dictionary of lists:
When each key is encountered for the first time, it is not already in the mapping; so an entry is automatically created using the default_factory function which returns an empty list. The list.append() operation then attaches the value to the new list. When keys are encountered again, the look-up proceeds normally (returning the list for that key) and the list.append() operation adds another value to the list. This technique is simpler and faster than an equivalent technique using dict.setdefault():
Setting the default_factory to int makes the defaultdict useful for counting (like a bag or multiset in other languages):
When a letter is first encountered, it is missing from the mapping, so the default_factory function calls int() to supply a default count of zero. The increment operation then builds up the count for each letter.
The function int() which always returns zero is just a special case of constant functions. A faster and more flexible way to create constant functions is to use a lambda function which can supply any constant value (not just zero):
Setting the default_factory to set makes the defaultdict useful for building a dictionary of sets:
Named tuples assign meaning to each position in a tuple and allow for more readable, self-documenting code. They can be used wherever regular tuples are used, and they add the ability to access fields by name instead of position index.
Returns a new tuple subclass named typename. The new subclass is used to create tuple-like objects that have fields accessible by attribute lookup as well as being indexable and iterable. Instances of the subclass also have a helpful docstring (with typename and field_names) and a helpful __repr__() method which lists the tuple contents in a name=value format.
The field_names are a sequence of strings such as ['x', 'y']. Alternatively, field_names can be a single string with each fieldname separated by whitespace and/or commas, for example 'x y' or 'x, y'.
Any valid Python identifier may be used for a fieldname except for names starting with an underscore. Valid identifiers consist of letters, digits, and underscores but do not start with a digit or underscore and cannot be a keyword such as class, for, return, global, pass, or raise.
If rename is true, invalid fieldnames are automatically replaced with positional names. For example, ['abc', 'def', 'ghi', 'abc'] is converted to ['abc', '_1', 'ghi', '_3'], eliminating the keyword def and the duplicate fieldname abc.
defaults can be None or an iterable of default values. Since fields with a default value must come after any fields without a default, the defaults are applied to the rightmost parameters. For example, if the fieldnames are ['x', 'y', 'z'] and the defaults are (1, 2), then x will be a required argument, y will default to 1, and z will default to 2.
If module is defined, the __module__ attribute of the named tuple is set to that value.
Named tuple instances do not have per-instance dictionaries, so they are lightweight and require no more memory than regular tuples.
To support pickling, the named tuple class should be assigned to a variable that matches typename.
Changed in version 3.1: Added support for rename.
Changed in version 3.6: The verbose and rename parameters became keyword-only arguments.
Changed in version 3.6: Added the module parameter.
Changed in version 3.7: Removed the verbose parameter and the _source attribute.
Changed in version 3.7: Added the defaults parameter and the _field_defaults attribute.
Named tuples are especially useful for assigning field names to result tuples returned by the csv or sqlite3 modules:
In addition to the methods inherited from tuples, named tuples support three additional methods and two attributes. To prevent conflicts with field names, the method and attribute names start with an underscore.
Class method that makes a new instance from an existing sequence or iterable.
Return a new dict which maps field names to their corresponding values:
Changed in version 3.1: Returns an OrderedDict instead of a regular dict.
Changed in version 3.8: Returns a regular dict instead of an OrderedDict. As of Python 3.7, regular dicts are guaranteed to be ordered. If the extra features of OrderedDict are required, the suggested remediation is to cast the result to the desired type: OrderedDict(nt._asdict()).
Return a new instance of the named tuple replacing specified fields with new values:
Tuple of strings listing the field names. Useful for introspection and for creating new named tuple types from existing named tuples.
Dictionary mapping field names to default values.
To retrieve a field whose name is stored in a string, use the getattr() function:
To convert a dictionary to a named tuple, use the double-star-operator (as described in Unpacking Argument Lists):
Since a named tuple is a regular Python class, it is easy to add or change functionality with a subclass. Here is how to add a calculated field and a fixed-width print format:
The subclass shown above sets __slots__ to an empty tuple. This helps keep memory requirements low by preventing the creation of instance dictionaries.
Subclassing is not useful for adding new, stored fields. Instead, simply create a new named tuple type from the _fields attribute:
Docstrings can be customized by making direct assignments to the __doc__ fields:
Changed in version 3.5: Property docstrings became writeable.
See also
See typing.NamedTuple for a way to add type hints for named tuples. It also provides an elegant notation using the class keyword:
Ordered dictionaries are just like regular dictionaries but have some extra capabilities relating to ordering operations. They have become less important now that the built-in dict class gained the ability to remember insertion order (this new behavior became guaranteed in Python 3.7).
Some differences from dict still remain:
Return an instance of a dict subclass that has methods specialized for rearranging dictionary order.
New in version 3.1.
The popitem() method for ordered dictionaries returns and removes a (key, value) pair. The pairs are returned in LIFO order if last is true or FIFO order if false.
Move an existing key to either end of an ordered dictionary. The item is moved to the right end if last is true (the default) or to the beginning if last is false. Raises KeyError if the key does not exist:
New in version 3.2.
In addition to the usual mapping methods, ordered dictionaries also support reverse iteration using reversed().
Equality tests between OrderedDict objects are order-sensitive and are implemented as list(od1.items())==list(od2.items()). Equality tests between OrderedDict objects and other Mapping objects are order-insensitive like regular dictionaries. This allows OrderedDict objects to be substituted anywhere a regular dictionary is used.
Changed in version 3.5: The items, keys, and values views of OrderedDict now support reverse iteration using reversed().
Changed in version 3.6: With the acceptance of PEP 468, order is retained for keyword arguments passed to the OrderedDict constructor and its update() method.
Changed in version 3.9: Added merge (|) and update (|=) operators, specified in PEP 584.
It is straightforward to create an ordered dictionary variant that remembers the order the keys were last inserted. If a new entry overwrites an existing entry, the original insertion position is changed and moved to the end:
An OrderedDict would also be useful for implementing variants of functools.lru_cache():
The class, UserDict acts as a wrapper around dictionary objects. The need for this class has been partially supplanted by the ability to subclass directly from dict; however, this class can be easier to work with because the underlying dictionary is accessible as an attribute.
Class that simulates a dictionary. The instance’s contents are kept in a regular dictionary, which is accessible via the data attribute of UserDict instances. If initialdata is provided, data is initialized with its contents; note that a reference to initialdata will not be kept, allowing it be used for other purposes.
In addition to supporting the methods and operations of mappings, UserDict instances provide the following attribute:
A real dictionary used to store the contents of the UserDict class.
This class acts as a wrapper around list objects. It is a useful base class for your own list-like classes which can inherit from them and override existing methods or add new ones. In this way, one can add new behaviors to lists.
The need for this class has been partially supplanted by the ability to subclass directly from list; however, this class can be easier to work with because the underlying list is accessible as an attribute.
Class that simulates a list. The instance’s contents are kept in a regular list, which is accessible via the data attribute of UserList instances. The instance’s contents are initially set to a copy of list, defaulting to the empty list []. list can be any iterable, for example a real Python list or a UserList object.
In addition to supporting the methods and operations of mutable sequences, UserList instances provide the following attribute:
A real list object used to store the contents of the UserList class.
Subclassing requirements: Subclasses of UserList are expected to offer a constructor which can be called with either no arguments or one argument. List operations which return a new sequence attempt to create an instance of the actual implementation class. To do so, it assumes that the constructor can be called with a single parameter, which is a sequence object used as a data source.
If a derived class does not wish to comply with this requirement, all of the special methods supported by this class will need to be overridden; please consult the sources for information about the methods which need to be provided in that case.
The class, UserString acts as a wrapper around string objects. The need for this class has been partially supplanted by the ability to subclass directly from str; however, this class can be easier to work with because the underlying string is accessible as an attribute.
Class that simulates a string object. The instance’s content is kept in a regular string object, which is accessible via the data attribute of UserString instances. The instance’s contents are initially set to a copy of seq. The seq argument can be any object which can be converted into a string using the built-in str() function.
In addition to supporting the methods and operations of strings, UserString instances provide the following attribute:
A real str object used to store the contents of the UserString class.
Changed in version 3.5: New methods __getnewargs__, __rmod__, casefold, format_map, isprintable, and maketrans.


New in version 3.3: Formerly, this module was part of the collections module.
Source code: Lib/_collections_abc.py
This module provides abstract base classes that can be used to test whether a class provides a particular interface; for example, whether it is hashable or whether it is a mapping.
The collections module offers the following ABCs:
ABC
Inherits from
Abstract Methods
Mixin Methods
Container
__contains__
Hashable
__hash__
Iterable
__iter__
Iterator
Iterable
__next__
__iter__
Reversible
Iterable
__reversed__
Generator
Iterator
send, throw
close, __iter__, __next__
Sized
__len__
Callable
__call__
Collection
Sized, Iterable, Container
__contains__, __iter__, __len__
Sequence
Reversible, Collection
__getitem__, __len__
__contains__, __iter__, __reversed__, index, and count
MutableSequence
Sequence
__getitem__, __setitem__, __delitem__, __len__, insert
Inherited Sequence methods and append, reverse, extend, pop, remove, and __iadd__
ByteString
Sequence
__getitem__, __len__
Inherited Sequence methods
Set
Collection
__contains__, __iter__, __len__
__le__, __lt__, __eq__, __ne__, __gt__, __ge__, __and__, __or__, __sub__, __xor__, and isdisjoint
MutableSet
Set
__contains__, __iter__, __len__, add, discard
Inherited Set methods and clear, pop, remove, __ior__, __iand__, __ixor__, and __isub__
Mapping
Collection
__getitem__, __iter__, __len__
__contains__, keys, items, values, get, __eq__, and __ne__
MutableMapping
Mapping
__getitem__, __setitem__, __delitem__, __iter__, __len__
Inherited Mapping methods and pop, popitem, clear, update, and setdefault
MappingView
Sized
__len__
ItemsView
MappingView, Set
__contains__, __iter__
KeysView
MappingView, Set
__contains__, __iter__
ValuesView
MappingView, Collection
__contains__, __iter__
Awaitable
__await__
Coroutine
Awaitable
send, throw
close
AsyncIterable
__aiter__
AsyncIterator
AsyncIterable
__anext__
__aiter__
AsyncGenerator
AsyncIterator
asend, athrow
aclose, __aiter__, __anext__
ABC for classes that provide the __contains__() method.
ABC for classes that provide the __hash__() method.
ABC for classes that provide the __len__() method.
ABC for classes that provide the __call__() method.
ABC for classes that provide the __iter__() method.
Checking isinstance(obj, Iterable) detects classes that are registered as Iterable or that have an __iter__() method, but it does not detect classes that iterate with the __getitem__() method. The only reliable way to determine whether an object is iterable is to call iter(obj).
ABC for sized iterable container classes.
New in version 3.6.
ABC for classes that provide the __iter__() and __next__() methods. See also the definition of iterator.
ABC for iterable classes that also provide the __reversed__() method.
New in version 3.6.
ABC for generator classes that implement the protocol defined in PEP 342 that extends iterators with the send(), throw() and close() methods. See also the definition of generator.
New in version 3.5.
ABCs for read-only and mutable sequences.
Implementation note: Some of the mixin methods, such as __iter__(), __reversed__() and index(), make repeated calls to the underlying __getitem__() method. Consequently, if __getitem__() is implemented with constant access speed, the mixin methods will have linear performance; however, if the underlying method is linear (as it would be with a linked list), the mixins will have quadratic performance and will likely need to be overridden.
Changed in version 3.5: The index() method added support for stop and start arguments.
ABCs for read-only and mutable sets.
ABCs for read-only and mutable mappings.
ABCs for mapping, items, keys, and values views.
ABC for awaitable objects, which can be used in await expressions. Custom implementations must provide the __await__() method.
Coroutine objects and instances of the Coroutine ABC are all instances of this ABC.
Note
In CPython, generator-based coroutines (generators decorated with types.coroutine() or asyncio.coroutine()) are awaitables, even though they do not have an __await__() method. Using isinstance(gencoro, Awaitable) for them will return False. Use inspect.isawaitable() to detect them.
New in version 3.5.
ABC for coroutine compatible classes. These implement the following methods, defined in Coroutine Objects: send(), throw(), and close(). Custom implementations must also implement __await__(). All Coroutine instances are also instances of Awaitable. See also the definition of coroutine.
Note
In CPython, generator-based coroutines (generators decorated with types.coroutine() or asyncio.coroutine()) are awaitables, even though they do not have an __await__() method. Using isinstance(gencoro, Coroutine) for them will return False. Use inspect.isawaitable() to detect them.
New in version 3.5.
ABC for classes that provide __aiter__ method. See also the definition of asynchronous iterable.
New in version 3.5.
ABC for classes that provide __aiter__ and __anext__ methods. See also the definition of asynchronous iterator.
New in version 3.5.
ABC for asynchronous generator classes that implement the protocol defined in PEP 525 and PEP 492.
New in version 3.6.
These ABCs allow us to ask classes or instances if they provide particular functionality, for example:
Several of the ABCs are also useful as mixins that make it easier to develop classes supporting container APIs. For example, to write a class supporting the full Set API, it is only necessary to supply the three underlying abstract methods: __contains__(), __iter__(), and __len__(). The ABC supplies the remaining methods such as __and__() and isdisjoint():
Notes on using Set and MutableSet as a mixin:
See also


ABC for asynchronous generator classes that implement the protocol defined in PEP 525 and PEP 492.
New in version 3.6.


ABC for classes that provide __aiter__ method. See also the definition of asynchronous iterable.
New in version 3.5.


ABC for classes that provide __aiter__ and __anext__ methods. See also the definition of asynchronous iterator.
New in version 3.5.


ABC for awaitable objects, which can be used in await expressions. Custom implementations must provide the __await__() method.
Coroutine objects and instances of the Coroutine ABC are all instances of this ABC.
Note
In CPython, generator-based coroutines (generators decorated with types.coroutine() or asyncio.coroutine()) are awaitables, even though they do not have an __await__() method. Using isinstance(gencoro, Awaitable) for them will return False. Use inspect.isawaitable() to detect them.
New in version 3.5.