Python Lex & Yacc

PLY (Python Lex-Yacc) is a pure-Python implementation of the lex and yacc tools commonly used to write parsers and compilers. It implements the LALR(1) parsing algorithm and offers extensive error reporting and diagnostic information. While version 3.11 is the latest stable release, the project's author announced its abandonment on December 21, 2025, with no further maintenance expected.