Hi list! Not long ago I was looking for an easy to use, but powerful parser and lexer generating tool for Python, and to my dismay, I found quite a number of Python projects implementing an (LA)LR(1) parser generator, but none of them seemed quite finished, or even pythonic.
As I required a parser generator for Python for one of my work projects, I set out to write (yet another one), and currently am at (release-)version 0.1 for Pyrr.ltk and ptk. An example for Pyrr.ltk and ptk usage implementing a (very) simple calculator: <<< # -*- coding: iso-8859-15 -*- from ltk import LexerBase, IgnoreMatch from ptk import ParserBase from operator import add, sub, mul, div class NumLexer(LexerBase): def number(self,value): """number -> r/[0-9]+/""" return float(value) def ws(self,*args): """ws -> r/\\s+/""" raise IgnoreMatch def ops(self,op): """addop -> /+/ -> /-/ mulop -> /*/ -> r/\\//""" return op class NumParser(ParserBase): """/mulop/: left /addop/: left""" __start__ = "term" def term(self,value1,op,value2): """term -> term /addop/ term -> term /mulop/ term""" return {"+":add,"-":sub,"*":mul,"/":div}[op](value1,value2) def value(self,value): """term -> /number/""" return value print NumParser.parse(NumLexer.tokenize("3 + 4 - 123 / 23")) <<< Grammar rules and lexemes are specified in docstrings, where lines not matching a definition of a rule or lexeme are ignored. The resulting lexer and parser class is, thus, very much self-documenting, which was one of my biggest goals for the project. I'm currently in the process of writing documentation for both packages (and especially documenting the extensions to BNF-grammars that Pyrr.ptk allows, such as your usual RE-operators ?, *, + and {x,y}, and forward arguments, and documenting the stateful lexer support that Pyrr.ltk implements), but I thought that I'd release early and often, so that people interested in this project might have a look at it now to input suggestions and extensions that they'd like me to add to make this a fully featured Python parser generating toolkit which might be offered as a Python package. Anyway, the sources can be downloaded (via subversion) from: http://svn.modelnine.org/svn/Pyrr/trunk where I'll check in the documentation that I've written so far and a Python distutils distribution over the weekend, and make sure that I don't check in brocken code from now on. And, Pyrr.* is Python 2.4 only at the moment, and I have no plans to make it backwards-compatible, but if you're interested in backporting it, feel free to mail me patches. --- Heiko. -- http://mail.python.org/mailman/listinfo/python-list