PLY

It provides most of the standard lex/yacc features including support for error recovery, empty productions, precedence rules, and support for ambiguous grammars.

PLY is extremely easy to use and provides very extensive error checking.

Features:

• It's implemented entirely in Python.
• It uses LR-parsing which is reasonably efficient and well suited for larger grammars.
• PLY provides most of the standard lex/yacc features including support for empty productions, precedence rules, error recovery, and support for ambiguous grammars.
• PLY is straightforward to use and provides very extensive error checking.
• PLY doesn't try to do anything more or less than provide the basic lex/yacc functionality. In other words, it's not a large parsing framework or a component of some larger system.

What is new in this release:

• Minor bug fixes for Python 3.2.

What is new in version 3.3:

• This is a minor bug-fix release.