Sample code for: Pyrefly: A Fast Static Type Checker for Python Projects

[lpozo]

Where to put new files:

• New files should go into a top-level subfolder, named after the article slug. For example: my-awesome-article

How to merge your changes:

1. Make sure the CI code style tests all pass (+ run the automatic code formatter if necessary).
2. Find an RP Team member on Slack and ask them to review & approve your PR.
3. Once the PR has one positive ("approved") review, GitHub lets you merge the PR.
4. 🎉

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Code examples for the Pyrefly: A Fast Static Type Checker for Python Projects tutorial. Files live in the pyrefly-python/ top-level folder, named after the article slug.

Generated from the tutorial markdown with the post-materials skill, then verified locally before pushing. Every file runs (except incorrect_types.py, which raises TypeError by design), and its pyrefly check results (Pyrefly 1.2.0, pinned in requirements.txt) match the tutorial.

🤖 Generated with Claude Code

[realpython-bot]

Final QA: verified all files run (incorrect_types.py raises TypeError by design), pyrefly 1.2.0 check/infer/coverage results match the tutorial, ruff format/check pass, README title and link correct.