Use this skill when preparing commits, running pre-commit hooks, checking code style, or validating changes before pushing. Covers PEP 7 (C code) and PEP 8 (Python) compliance, trailing whitespace rules, the no-type-annotations-in-Lib policy, and patchcheck validation. Note: patchcheck requires a build directory - load the `build` skill first if you haven't built CPython yet.
View on GitHubplugins/cpython-skills/skills/style/SKILL.md
January 21, 2026
Select agents to install to:
npx add-skill https://github.com/gpshead/cpython-skills/blob/main/plugins/cpython-skills/skills/style/SKILL.md -a claude-code --skill styleInstallation paths:
.claude/skills/style/# CPython Coding Style and Standards ## Style Guidelines **Python code** (`Lib/` etc): Follow PEP 8. Be consistent with nearby code. **C code** (`Modules/`, `Objects/`, `Python/`, `Include/`): Follow PEP 7. Be consistent with nearby code. ## Critical Rules **NEVER leave trailing whitespace on any line.** Pre-commit hooks will catch this. **ALWAYS preserve the final newline** at the end of files. **NEVER add type annotations to `Lib/` tree.** Stdlib doesn't use inline annotations (maintained in typeshed separately). Annotations may be OK in `Tools/` or test code if requested. **No autoformatting by default.** Only use `Doc/venv/bin/ruff format` if explicitly requested. ## Pre-Commit Workflow Before committing, run from repo root: ```bash # 1. Pre-commit hooks (checks whitespace, file endings, syntax) pre-commit run --all-files # 2. Patchcheck (MUST PASS - validates C/Python style, docs, whitespace) make -C $BUILD_DIR patchcheck # 3. If you modified Doc/, verify reStructuredText make -C Doc check # 4. Run relevant tests $BUILT_PY -m test test_yourmodule -j $(nproc) ``` ## Documentation - **Python docstrings**: Follow PEP 257, document params/returns/exceptions - **C comments**: Follow PEP 7, document complex algorithms - **reStructuredText** (`Doc/`): Follow Sphinx/reST conventions, verify with `make -C Doc check`