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

    • Using Lark to Parse Text - Robin Reynolds-Haertle (PyCascades 2023) (video presentation)

• 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)