LibCST

LibCST parses Python 3.0 -> 3.13 source code as a CST tree that keeps all formatting details (comments, whitespaces, parentheses, etc). It’s useful for building automated refactoring (codemod) applications and linters.

Introduction:

• Why LibCST?
  • Abstract Syntax Trees (AST)
  • Concrete Syntax Trees (CST)
  • LibCST
• Motivation
  • Exact Representation
  • Ease of Traversal
  • Ease of Modification
  • Well Tested

Tutorial:

• Parsing and Visitors
  • Parse Source Code
  • Display Source Code CST
  • Build Visitor or Transformer
  • Generate Source Code
• Metadata
  • Providing Metadata
  • Accessing Metadata
• Scope Analysis
  • Warn on unused imports and undefined references
  • Automatically Remove Unused Import
• Matchers
  • Basic Matcher Usage
  • Matcher Decorators
• Codemodding
  • Setting up and Running Codemods
  • Writing a Codemod
  • Testing Codemods
• Best Practices
  • Avoid isinstance when traversing
  • Prefer updated_node when modifying trees
  • Provide a config when generating code from templates

Reference:

• Parsing
  • parse_module()
  • parse_expression()
  • parse_statement()
  • PartialParserConfig
  • Syntax Errors
• Nodes
  • CSTNode
  • Module
  • Expressions
  • Statements
  • Operators
  • Miscellaneous
  • Whitespace
  • Maybe Sentinel
• Visitors
  • CSTVisitor
  • CSTTransformer
  • RemoveFromParent()
  • RemovalSentinel
  • FlattenSentinel
  • Visit and Leave Helper Functions
  • Traversal Order
  • Batched Visitors
• Metadata
  • Metadata APIs
  • Metadata Providers
• Matchers
  • Matcher APIs
  • Matcher Types
• Codemods
  • Codemod Base
  • Execution Interface
  • Command-Line Support
  • Command-Line Toolkit
  • Library of Transforms
• Helpers
  • Construction Helpers
  • Transformation Helpers
  • Traversing Helpers
  • Node fields filtering Helpers
• Experimental APIs
  • Reentrant Code Generation

Indices and tables

• Index

• Module Index

• Search Page

Privacy Policy and Terms of Use

• Privacy Policy

• Terms of Use