CPython Skills Marketplace

A Claude Code marketplace providing specialized skills for working with the CPython repository - the reference implementation of the Python programming language.

Overview

This marketplace hosts Claude Code plugins with AI-agent skills for CPython development. Currently includes one comprehensive plugin with multiple skills providing deep knowledge about CPython's codebase structure, build system, testing infrastructure, and coding standards.

Installation

To use these skills in Claude Code within a CPython repository checkout:

1. Add the marketplace:

   /plugin marketplace add gpshead/cpython-skills
   

2. Install the plugin:

   /plugin install cpython-skills
   

3. In your CPython repository, ask Claude:

   write a CLAUDE.local.md that instructs you to load and use all of the cpython-skills plugin in this repo.
   

Available Plugins

CPython Skills

Name: cpython-skills Description: Skills for working with the CPython repository - helping with building, testing, and contributing to Python's implementation

This plugin provides four specialized skills:

1. cpython-codebase

When to use: Working in the CPython repository, understanding codebase structure, managing engineering notebooks

Provides:

• Recommended tools (rg, gh, jq)
• Source code organization (Lib/, Modules/, Objects/, Python/, Include/)
• Test location and naming conventions
• Argument Clinic overview
• Engineering notebook management for PRs and branches as task-specific long term memory
• Scratch space usage
• Developer guide and PEP references

2. cpython-build-and-test

When to use: Configuring, building, rebuilding CPython, running tests, collecting coverage, debugging test failures

Includes:

• Build directory setup
• Platform-specific configuration (Linux, macOS, Windows)
• Incremental builds
• Argument Clinic code generation
• Build verification and troubleshooting
• unittest-based testing (not pytest!)
• Running individual tests and test suites
• Using --match for test filtering
• Code coverage collection
• Test package handling
• Interactive debugging with tmux

3. cpython-code-style

When to use: Writing code, ensuring style compliance, preparing commits

Covers:

• PEP 7 (C code) and PEP 8 (Python code) compliance
• Trailing whitespace and file ending rules
• Type annotation policy (no annotations in Lib/!)
• Pre-commit hooks and patchcheck
• Documentation formatting

4. cpython-docs

When to use: Working with CPython documentation, adding version markers, creating NEWS entries

Covers:

• Documentation in ReST format in Doc/ tree
• Documentation tooling setup and validation
• Version markers (always use next)
• NEWS file entries for bug fixes and features

Recommended Tools

These tools improve the agentic development experience: rg, gh, jq

Marketplace Structure

cpython-skills/
├── .claude-plugin/
│   └── marketplace.json    # Marketplace manifest
├── plugins/
│   └── cpython-skills/     # CPython skills plugin
│       ├── plugin.json     # Plugin manifest
│       └── skills/         # Individual skills
│           ├── cpython-codebase/
│           │   └── SKILL.md
│           ├── cpython-build-and-test/
│           │   └── SKILL.md
│           ├── cpython-code-style/
│           │   └── SKILL.md
│           └── cpython-docs/
│               └── SKILL.md
├── LICENSE
└── README.md               # This file

For Plugin Developers

Adding New Plugins to This Marketplace

To add a new plugin to this marketplace:

1. Create a new directory under plugins/ with your plugin name
2. Add your plugin files (skills, commands, agents, etc.)
3. Create a plugin.json manifest in your plugin directory
4. Update .claude-plugin/marketplace.json to include your plugin entry

Example marketplace.json plugin entry:

{
  "name": "your-plugin-name",
  "source": "./plugins/your-plugin-name",
  "description": "Brief description of what your plugin does"
}

Skills Format

This marketplace follows the Claude Skills specification, making plugins usable by any AI agent that supports this format.

Each skill is a self-contained directory with a SKILL.md file containing:

• YAML frontmatter with name and description
• Markdown content with detailed instructions

Usage Examples

When working with CPython, the AI agent will automatically:

1. Load cpython-codebase when starting work in the repo
2. Apply cpython-build-and-test knowledge when compiling or running tests
3. Enforce cpython-code-style rules when writing code
4. Follow cpython-docs guidance when updating documentation

Origin

This marketplace was created from the original CPython skills plugin, which was converted from the cpython/CLAUDE.local.md file. The marketplace-based approach provides:

• Modularity: Each skill focuses on a specific domain
• Discoverability: AI agents can find relevant skills based on task descriptions
• Reusability: Skills can be used independently or together
• Extensibility: Easy to add new plugins to the marketplace
• Interoperability: Works with any agent supporting Claude Skills format

License

CC0 1.0 Universal

References

• Claude Code Plugin Marketplaces Documentation
• Claude Code Plugins Documentation
• Claude Code Skills Documentation
• Simon Willison on Claude Skills
• CPython Developer Guide