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 five specialized skills:

1. cpython-context

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

Provides essential context including:

• Recommended tools (gh, ripgrep, jq, pre-commit)
• File size considerations
• Engineering notebook management for PRs and branches as a task specific long term memory
• Developer guide and PEP references

2. cpython-navigation

When to use: Finding code, understanding codebase structure, locating tests

Covers:

• Source code organization (Lib/, Modules/, Objects/, Python/, Include/)
• Test location and naming conventions
• Argument Clinic overview
• Scratch space usage
• Documentation structure

3. cpython-build

When to use: Configuring, building, or rebuilding CPython

Includes:

• Build directory setup
• Platform-specific configuration (Linux, macOS, Windows)
• Incremental builds
• Argument Clinic code generation
• Build verification and troubleshooting

4. cpython-testing

When to use: Running tests, collecting coverage, debugging test failures

Details:

• 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

5. 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

Recommended Tools

While the skills are designed to work with or without these tools, having them installed can significantly improve the agentic development experience:

ripgrep (rg)

Why: Significantly faster than grep or find for searching large codebases

• CPython has extensive C and Python source files
• ripgrep is optimized for source code searching with smart defaults
• Install: Most package managers have ripgrep (command is rg)

GitHub CLI (gh)

Why: Streamlined access to PR and issue information

• Query PR details, comments, and status directly from command line
• Use GraphQL API for complex queries
• Install: https://cli.github.com/
• You must manually pre-authorize this in line with your comfort level. For example, you could use a fine grained GitHub access token if you want to limit it to read-only access or only some of your repos if you are afraid of giving less trustworthy agents write access to interact with the world.

jq

Why: Process JSON responses from APIs and tools

• Parse and filter GitHub and other tool and API responses
• Process structured tool output
• Install: Available in most package managers

pre-commit

Why: Automated code quality checks before commits

• Catches trailing whitespace, file endings, and syntax errors
• Runs configured linters and formatters
• Prevents common mistakes from being committed
• Install: pip install pre-commit or via package manager

Note: The skills gracefully handle missing tools, but will recommend installation when relevant tasks arise.

Marketplace Structure

cpython-skills/
├── .claude-plugin/
│   └── marketplace.json    # Marketplace manifest
├── plugins/
│   └── cpython-skills/     # CPython skills plugin
│       ├── plugin.json     # Plugin manifest
│       └── skills/         # Individual skills
│           ├── cpython-context/
│           │   └── SKILL.md
│           ├── cpython-navigation/
│           │   └── SKILL.md
│           ├── cpython-build/
│           │   └── SKILL.md
│           ├── cpython-testing/
│           │   └── SKILL.md
│           └── cpython-code-style/
│               └── 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-context when starting work in the repo
2. Use cpython-navigation to find relevant source files
3. Apply cpython-build knowledge when compiling
4. Follow cpython-testing guidance when running tests
5. Enforce cpython-code-style rules when writing code

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