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python4ply 1.0

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\w+) *(?P\(.*\)) *:/:
        print repr($1), repr($args)

The primary site for ply4python is http://dalkescientific.com/Python/python4ply.html. The package is released under the MIT license.

Download python4ply-1.0.tar.gz or view the tutorial.