lark-parser/lark

Health v2 · maintenance only

Adoption not part of the score

5968 stars · 512 forks observed · 2026-08-28

What it is AI-extracted, prompt v1, taxonomy v1, 2026-08-29, confidence not recorded

Lark is a parsing toolkit for Python that can parse all context-free grammars using Earley, LALR(1), and CYK algorithms. It automatically builds annotated parse trees from a grammar and input, with no construction code required.

Use cases

• parse a custom DSL in python
• build a json parser from a grammar
• parse config files into a syntax tree
• write a parser for a programming language
• handle ambiguous grammars gracefully
• generate a standalone parser for distribution
• build an AST from source code

When to choose

• you need to parse any context-free grammar, including ambiguous ones
• you want automatic parse-tree construction without writing tree-building code
• you want a pure-python, dependency-free parser that runs on any Python interpreter
• you want to trade off parsing power and speed (Earley vs LALR)

When to avoid

• you need maximum parsing speed in a performance-critical system (a compiled-language parser will be faster)
• you need a parser generator for languages other than Python
• your grammar requires context-sensitive parsing beyond context-free

Facets

library · maturity stable

parser interpreter parsers programming-languages developer-tools python cross-platform earley lalr context-free-grammars parse-tree dsl pure-python standalone-parser-generation

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