Ply python lex yacc

PLY (Python Lex-Yacc)¶

PLY requires the use of Python 3.6 or greater. Older versions of Python are not supported.

Overview¶

PLY is a 100% Python implementation of the lex and yacc tools commonly used to write parsers and compilers. Parsing is based on the same LALR(1) algorithm used by many yacc tools. Here are a few notable features:

• PLY provides very extensive error reporting and diagnostic information to assist in parser construction. The original implementation was developed for instructional purposes. As a result, the system tries to identify the most common types of errors made by novice users.
• PLY provides full support for empty productions, error recovery, precedence specifiers, and moderately ambiguous grammars.
• PLY can be used to build parsers for “real” programming languages. Although it is not ultra-fast due to its Python implementation, PLY can be used to parse grammars consisting of several hundred rules (as might be found for a language like C).

More Documentation¶

• PLY (Python Lex-Yacc)
  • Introduction
  • PLY Overview
  • Lex
    • Lex Example
    • The tokens list
    • Specification of tokens
    • Token values
    • Discarded tokens
    • Line numbers and positional information
    • Ignored characters
    • Literal characters
    • Error handling
    • EOF Handling
    • Building and using the lexer
    • The @TOKEN decorator
    • Debugging
    • Alternative specification of lexers
    • Maintaining state
    • Lexer cloning
    • Internal lexer state
    • Conditional lexing and start conditions
    • Miscellaneous Issues
    • An example
    • Combining Grammar Rule Functions
    • Character Literals
    • Empty Productions
    • Changing the starting symbol
    • Dealing With Ambiguous Grammars
    • The parser.out file
    • Syntax Error Handling
    • Line Number and Position Tracking
    • AST Construction
    • Embedded Actions
    • Miscellaneous Yacc Notes
    • Debugging the lex() and yacc() commands
    • Run-time Debugging
    • 1. Introduction
    • 2. Grammar Class
    • 3. Productions
    • 4. LRItems
    • 5. LRTable
    • 6. LRParser
    • 7. ParserReflect
    • 8. High-level operation

    Resources¶

    For a detailed overview of parsing theory, consult the excellent book “Compilers : Principles, Techniques, and Tools” by Aho, Sethi, and Ullman. The topics found in “Lex & Yacc” by Levine, Mason, and Brown may also be useful.

    The GitHub page for PLY can be found at:

    Please direct bug reports and pull requests to the GitHub page. To contact me directly, send email to dave @ dabeaz . com or contact me on Twitter (@dabeaz).

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