Package: pypre
A python preprocessorThis package is meant to pre-process raw python 3 files.Usagepypre [ -i INPUT_FILE or --input INPUT_FILE ] [ -o OUTPUT_FILE --output OUTPUT_FILE ]If an input file is not given, pypre will read input on stdin.
Likewise, if an output file is notgiven, pypre will write output to stdout.SyntaxThe syntax for the preprocessor is fairly simple:#define <CONST> [<VALUE>]This defines a new constant name “CONST”, optionally with the
value “VALUE”. If a VALUE is not specified, “CONST” will be
assigned the valueNone. “VALUE”mustbe a python literal
value. The primitive objects currently supported are:intfloatstrbytesThis also includes the following primitive collections of
these types:listtupledictsetFinally, valuesMUSTbe literal. pypre cannot and will not
interpret#defines that include#defined constant
names.
Just like the C/C++ preprocessor, anywhere a#defined
constant is found within the source code (except on lines
containing directives) it will be replaced with its value.WARNING:This does not yet check whether names are inside of
string literals or comments.#undef <CONST>Removes the definition of the name specified by “CONST”. If the
name wasn’t defined in the first place, nothing happens (or at
least it shouldn’t).#ifdef <CONST>Begins a block of conditionally-compiled code. All code up to the
matching terminator will be included in the output if and only if
the constant named by “CONST” has been defined. (see#endif)#ifndef <CONST>Provided mainly for historical reasons, this begins a block of
conditionally-compiled code similar to#ifdef, but will
include the enclosed block if and only if the named constant
“CONST” isnotdefined.#if <EXPR>The real meat of pypre. This begins a block of
conditionally-compiled code based on the truth-y value of “EXPR”.
“EXPR” can take two forms. In the first form, it takes a single
value. It can be - somewhat uselessly - a python literal that
would be valid as the “VALUE” of a#define, or it can be the
name of a previously-#defined value. In its second form,
“EXPR” looks like:<VALUE> <OP> <VALUE>Where each “VALUE” is
anything that would be valid for a “VALUE” in the first form, and
“OP” is a boolean operator. Valid operators and their definition
are:=The Equality Operator - tests that the two values are
equal.!The Inequality Operator - tests that the two values are
NOT equal.<The Less-Than Operator - tests that the first value is
strictly less than the second.>The Greater-Than Operator - tests that the first value is
strictly greater than the second.#elseIf found within a block of conditionally-compiled code, will
begin a section of conditionally-code that will be included if
and only if the lines between the directive that started the
block and the line containing#elsearenotincluded.#endifEnds a block of conditionally-compiled code. For every#if,#ifdefandifndef, there must be exactly one#endif.Guaranteed ValuesThe following values are defined at runtime, and can be overridden
with an environment variableof the same name:PYTHON_VERSIONA tuple of the form “(MAJOR, MINOR, MICRO)” where each element is
of typeint. It will default to the version information of
the interpreter used to run pypre. Setting this will setPYTHON_MAJOR_VERSION,PYTHON_MINOR_VERSION, andPYTHON_MICRO_VERSIONaccordingly.PYTHON_MAJOR_VERSIONAnintrepresenting a Python major version number. Will
default to the major version number of the interpreter used to
run pypre. If you set this variable through the environment
variable of the same name, it will setPYTHON_MINOR_VERSIONandPYTHON_MICRO_VERSIONboth to0(unless those are set
as well, in which case they will use their defined values).PYTHON_MINOR_VERSIONAnintrepresenting a Python minor version number. Will
default to the minor version number of the interpreter used to
run pypre. If you set this variable through the environment
variable of the same name, it will setPYTHON_MAJOR_VERSIONto3andPYTHON_MICRO_VERSIONto0. (unless those are
set as well, in which case they will use their defined values).PYTHON_MICRO_VERSIONAnintrepresenting a Python micro version number. Will
default to the micro version number of the interpreter used to
run pypre. If you set this variable through the environment
variable of the same name, it will setPYTHON_MAJOR_VERSIONto3andPYTHON_MINOR_VERSIONto0. (unless those are
set as well, in which case they will use their defined values).PYTHON_IMPLEMENTATIONAstrthat names the Python implementation. Defaults to the
output ofplatform.python_implementation(). Some examples
include: ‘CPython’, ‘IronPython’, ‘Jython’, ‘PyPy’.OSAstrnaming the operating system. Defaults to thesysnamepart of the output ofos.uname().ARCHA string specifying the system’s architecture. Defaults to the
output ofplatform.machine()IS64True if the host processor is 64-bit, otherwise False. Default is
determined using thebitspart of the output ofplatform.architecture().__DATE__A literalstrcontaining the date on which the pre-processing
is occurring, in the same format as the C++ macro of the same
name: “Mmm dd yyyy”. The default value is obtained from the
output oftime.strftime("%b%d %Y").__TIME__A literalstrcontaining the local time at which the
pre-processing is occurring, in the same format as the C++ macro
of the same name: “hh:mm:ss”. The default value is obtained from
the output oftime.strftime("%H:%M:%S").__IPV6__Trueif the system supports IPv6 addressing,Falseotherwise. Default value is obtained from the value ofsocket.has_ipv6.__BYTE_ORDER__This is a value representing the native byte order of the host
machine. Its default value is calculated using thestructlibrary and it has no particular guaranteed value. The only thing
that can be depended upon is that it will be equal to either__BIG_ENDIAN__or__LITTLE_ENDIAN__; never both and never
neither.Implementation Note:As of the time of this writing,__BIG_ENDIAN__is set to the value1and__LITTLE_ENDIAN__is set to the value0. This is subject
to change as I may need to specify the endian-ness of bits or
gods only knows what else in the future.Note that if you do choose to override these values, you MUST match
their type. For example, ifthe nameFOOis provided with a value of (b’\x69’, 15.2), you
must provide a value that is a2-tuple of the form (bytes,float). In bash, this example
would look like:FOO="(b'my overridden bytes', -1.1)"pypreSome caveats and disclaimers:Do not use spaces in your names or values (except between elements in
collections) as this will instantly crash the preprocessor.pypre is only built for, and only tested against Python 3 versions.
Don’t be surprised if it doesn’t work if run through your Python 2
interpreter. (Note that you can easily include pypre directives in
Python 2 code as long as pypre itself is run through Python 3,
although it will require you to setPYTHON_VERSIONyourself if
you plan to use it.)SettingPYTHON_VERSIONand one of the more specific
“MAJOR”/”MINOR”/”MICRO” variables to non-compatible values will cause
the preprocessor to immediately exit. For example, you can’t havePYTHON_VERSION=(2,7,0)andPYTHON_MAJOR_VERSION=3- be sure
your environment makes sense.