PLY is yet another implementation of lex and yacc for Python.
Although several other parsing tools are available for Python,
there are several reasons why you might want to take a look at
PLY: - 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 extremely easy to use and provides very extensive error
checking.