You're adding type hints to your Python code, your editor is happy, autocomplete is working great. But then you switch tools and suddenly there are red squiggles everywhere. Who decides what a float annotation actually means? Or whether passing None where an int is expected should be an error? It turns out there's a five-person council dedicated to exactly these questions -- and two brand-new Rust-based type checkers are raising the bar. On this episode, I sit down with three members of the Python Typing Council -- Jelle Zijlstra, Rebecca Chen, and Carl Meyer -- to learn how the type system is governed, where the spec and the type checkers agree and disagree, and get the council's official advice on how much typing is just enough.

Episode sponsors

Sentry Error Monitoring, Code talkpython26
Agentic AI Course
Talk Python Courses

Links from the show

Guests
Carl Meyer: github.com
Jelle Zijlstra: jellezijlstra.github.io
Rebecca Chen: github.com

Typing Council: github.com
typing.python.org: typing.python.org
details here: github.com
ty: docs.astral.sh
pyrefly: pyrefly.org
conformance test suite project: github.com
typeshed: github.com
Stub files: mypy.readthedocs.io
Pydantic: pydantic.dev
Beartype: github.com
TOAD AI: github.com
PEP 747 – Annotating Type Forms: peps.python.org
PEP 724 – Stricter Type Guards: peps.python.org
Python Typing Repo (PRs and Issues): github.com

Watch this episode on YouTube: youtube.com
Episode #539 deep-dive: talkpython.fm/539
Episode transcripts: talkpython.fm

Theme Song: Developer Rap
🥁 Served in a Flask 🎸: talkpython.fm/flasksong

---== Don't be a stranger ==---
YouTube: youtube.com/@talkpython

Bluesky: @talkpython.fm
Mastodon: @talkpython@fosstodon.org
X.com: @talkpython

Michael on Bluesky: @mkennedy.codes
Michael on Mastodon: @mkennedy@fosstodon.org
Michael on X.com: @mkennedy

#539: Catching up with the Python Typing Council