Features

Main Features

• Earley parser, capable of parsing any context-free grammar

  • Implements SPPF, for efficient parsing and storing of ambiguous grammars.

• LALR(1) parser, limited in power of expression, but very efficient in space and performance (O(n)).

  • Implements a parse-aware lexer that provides a better power of expression than traditional LALR implementations (such as ply).

• EBNF-inspired grammar, with extra features (See: Grammar Reference)

• Builds a parse-tree (AST) automagically based on the grammar

• Stand-alone parser generator - create a small independent parser to embed in your project. (read more)

• Flexible error handling by using an interactive parser interface (LALR only)

• Automatic line & column tracking (for both tokens and matched rules)

• Automatic terminal collision resolution

• Warns on regex collisions using the optional interegular library. (read more)

• Grammar composition - Import terminals and rules from other grammars (see example).

• Standard library of terminals (strings, numbers, names, etc.)

• Unicode fully supported

• Extensive test suite

• Type annotations (MyPy support)

• Pure-Python implementation

Read more about the parsers

Extra features

• Support for external regex module (see here)

• Import grammars from Nearley.js (read more)

• CYK parser

• Visualize your parse trees as dot or png files (see_example)

• Automatic reconstruction of input from parse-tree (see example and another example)

• Use Lark grammars in Julia and Javascript.