Welcome to Lark’s documentation!

Lark is a modern parsing library for Python. Lark can parse any context-free grammar.

Lark provides:

• Advanced grammar language, based on EBNF
• Three parsing algorithms to choose from: Earley, LALR(1) and CYK
• Automatic tree construction, inferred from your grammar
• Fast unicode lexer with regexp support, and automatic line-counting

Install Lark

$ pip install lark

Syntax Highlighting

• Sublime Text & TextMate
• Visual Studio Code (Or install through the vscode plugin system)
• Intellij & PyCharm
• Vim
• Atom

Resources

• Philosophy
• Features
• Examples
• Third-party examples
• Online IDE
• Tutorials
  • How to write a DSL - Implements a toy LOGO-like language with an interpreter
  • JSON parser - Tutorial - Teaches you how to use Lark
  • Unofficial
    • Program Synthesis is Possible - Creates a DSL for Z3
• Guides
  • How To Use Lark - Guide
  • How to develop Lark - Guide
• Reference
  • Grammar Reference
  • Tree Construction Reference
  • Transformers & Visitors
  • Working with the SPPF
  • API Reference
  • Tools (Stand-alone, Nearley)
  • Cheatsheet (PDF)
• Discussion
  • Gitter
  • Forum (Google Groups)