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python4ply

python4ply is a Python parser for the Python language. The grammar definition uses PLY, a parser system for Python modelled on yacc/lex. The parser rules use the "compiler" module from the standard library to build a Python AST and to generate byte code for .pyc file.

You might use python4ply to experiment with variations in the Python language. The PLY-based lexer and parser are much easier to change than the C implementation Python itself uses or even the ones written in Python which are part of the standard library. This tutorial walks through examples of how to make changes in different levels of the system

To give you an idea of what it can do, here are some examples from the tutorial:

     # integers with optional underscores separators 
amount = 20_000_000
print "You owe me", amount, "dollars"
      # sytax-level support for decimals
% cat div.py
# div.py
print "float", 1.0 % 0.1
print "decimal", 0d1.0 % 0d0.1
% python compile.py -e div.py
float 0.1
decimal 0.0
% 
      # Perl-like regex creation and match operator
for line in open("python_yacc.py"):
    if line =~ m/def (?P<name>\w+) *(?P<args>\(.*\)) *:/:
        print repr($1), repr($args)

Links

License


(This is the MIT License with the serial numbers scratched off and my
name written in in crayon.  I would prefer "share and enjoy" but
apparently that isn't a legally acceptable.)

Copyright (c) 2008 Andrew Dalke 
Dalke Scientific Software, AB

Permission is hereby granted, free of charge, to any person obtaining
a copy of this software and associated documentation files (the
"Software"), to deal in the Software without restriction, including
without limitation the rights to use, copy, modify, merge, publish,
distribute, sublicense, and/or sell copies of the Software, and to
permit persons to whom the Software is furnished to do so, subject to
the following conditions:

The above copyright notice and this permission notice shall be
included in all copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE
LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION
OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.

See Also

EasyExtend - "a system for creating extension languages for Python"



Copyright © 2001-2013 Andrew Dalke Scientific AB