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Description:

pypre 0.3.0

A python preprocessor
This package is meant to pre-process raw python 3 files.

Usage
pypre [ -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 not
given, pypre will write output to stdout.

Syntax
The 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 value None. “VALUE” must be a python literal
value. The primitive objects currently supported are:

int
float
str
bytes
This also includes the following primitive collections of
these types:
list
tuple
dict
set
Finally, values MUST be 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” is not defined.

#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.

#else

If 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 #else are not included.

#endif

Ends a block of conditionally-compiled code. For every #if,
#ifdef and ifndef, there must be exactly one #endif.

Guaranteed Values

The following values are defined at runtime, and can be overridden
with an environment variable
of the same name:

PYTHON_VERSION

A tuple of the form “(MAJOR, MINOR, MICRO)” where each element is
of type int. It will default to the version information of
the interpreter used to run pypre. Setting this will set
PYTHON_MAJOR_VERSION, PYTHON_MINOR_VERSION, and
PYTHON_MICRO_VERSION accordingly.

PYTHON_MAJOR_VERSION

An int representing 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 set PYTHON_MINOR_VERSION
and PYTHON_MICRO_VERSION both to 0 (unless those are set
as well, in which case they will use their defined values).

PYTHON_MINOR_VERSION

An int representing 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 set PYTHON_MAJOR_VERSION
to 3 and PYTHON_MICRO_VERSION to 0. (unless those are
set as well, in which case they will use their defined values).

PYTHON_MICRO_VERSION

An int representing 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 set PYTHON_MAJOR_VERSION
to 3 and PYTHON_MINOR_VERSION to 0. (unless those are
set as well, in which case they will use their defined values).

PYTHON_IMPLEMENTATION

A str that names the Python implementation. Defaults to the
output of platform.python_implementation(). Some examples
include: ‘CPython’, ‘IronPython’, ‘Jython’, ‘PyPy’.

OS

A str naming the operating system. Defaults to the
sysname part of the output of os.uname().

ARCH

A string specifying the system’s architecture. Defaults to the
output of platform.machine()

IS64

True if the host processor is 64-bit, otherwise False. Default is
determined using the bits part of the output of
platform.architecture().

__DATE__

A literal str containing 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 of time.strftime("%b %d %Y").

__TIME__

A literal str containing 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 of time.strftime("%H:%M:%S").

__IPV6__

True if the system supports IPv6 addressing, False
otherwise. Default value is obtained from the value of
socket.has_ipv6.

__BYTE_ORDER__

This is a value representing the native byte order of the host
machine. Its default value is calculated using the struct
library 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 value 1 and
__LITTLE_ENDIAN__ is set to the value 0. 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, if
the name FOO is provided with a value of (b’\x69’, 15.2), you
must provide a value that is a
2-tuple of the form (bytes, float). In bash, this example
would look like:

FOO="(b'my overridden bytes', -1.1)" pypre

Some 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 set PYTHON_VERSION yourself if
you plan to use it.)
Setting PYTHON_VERSION and 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 have
PYTHON_VERSION=(2,7,0) and PYTHON_MAJOR_VERSION=3 - be sure
your environment makes sense.