# Python Typing Reference

> Answer detailed or normative questions about Python's type system using the complete vendored typing specification. Use for subtle assignability, generics, variance, protocols, overloads, narrowing, qualifiers, TypedDict, or checker-semantics questions that exceed everyday annotation guidance.

- Skill: `cjthompson/python-typing-reference` (Agent Skill, multi-file: 2 files)
- Install (CLI): `npx skillmds@latest add cjthompson/python-typing-reference`
- Raw SKILL.md: https://api.skillmd.com/api/skills/cjthompson/python-typing-reference/raw
- Safety review: PASS (external: skill-scanner PASS, skillspector PASS)
- Works with: Claude Code, Claude.ai, OpenAI Codex
- Category: Coding & Dev Tools
- Author: cjthompson (https://skillmd.com/u/cjthompson)
- Updated: 2026-08-19
- Page: https://skillmd.com/skills/cjthompson/python-typing-reference

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# Python Typing Reference

Use the vendored specification as the authority rather than relying on recollection.

1. Read `references/topic-index.md` to select the smallest relevant specification files.
2. Read those files under `../../vendor/typing-spec/` completely enough to capture definitions, rules, examples, and exceptions.
3. Distinguish normative typing rules from a particular checker's implementation or extension.
4. State version-sensitive assumptions and use the project's declared Python version and checker.
5. Explain the result with the smallest useful example and name the source files consulted.