Ty – A fast Python type checker, written in Rust
docs.astral.shBuried as a dupe for now, until a release post is published. See https://news.ycombinator.com/item?id=46101669 for more.
Previous discussion:
Ty: A fast Python type checker and language server - https://news.ycombinator.com/item?id=43918484 - May 2025 (287 comments)
I'm not sure if they're gearing up for an announcement, but about 9 days ago they dropped the preview warning from their README. I'm assuming they're still working through final housekeeping items before formally announcing it.
[1] https://github.com/astral-sh/ty/commit/7a6b79d37e165f2e73189...
I mean, it's been announced already. Caveat: It's still very far from being competitive with SOTA type checkers like basedpyright.
Still, it's great that this is being worked on and I expect in a year or two ty should be comprehensive enough to migrate over to.
Facebook's pyrefly might be the one part that could break up astral's total python ecosystem dominance, and that is probably a good thing.
I'm saying that as a massive uv and ruff fan.
I would hesitate to call it total dominance. There's a lot of good competition arising in this space. If you haven't already, check out pixi for example. And yeah, pyrefly is fantastic.
Competition is good in this case.
Why is that a good thing?
I don't think that the whole ecosystem should be dominated by a single VC backed startup.
I want my tools to be interchangeable and to play well with other choices.
Having multiple big players helps with that.
Maybe I'm wrong on this, but I rather have 1 tool everyone else is using. Cargo in Rust ecosystem works really well, everyone loves it.
Imagine if Cargo was not first-party, but a third-party tool belonging to a vc startup with zero revenue.
Then that startup makes rustup, rustfmt and rust-analyzer. Great, but I would be more comfortable with the ecosystem if at least the rust-analyzer and rustfmt parts had competitive alternatives.
previous discussion: https://news.ycombinator.com/item?id=43918484
my understanding is no real news on Ty since then? is Astral announcing it as production ready?
Charlie Marsh tweeted 7 hours ago "ty is coming" - https://x.com/charliermarsh/status/1995153742040330467
Then "Release post will cover all of this" in reply to a question asking for a detailed comparison to alternatives: https://x.com/charliermarsh/status/1995163183808643466
Given that there is no release post yet, I think it's best to bury this submission as a dupe. When the release post is published, that will count as "significant new information", which is a valid trigger for a new discussion on HN.
How long until these guys make a great transpiler to Rust?
I’m half kidding.
Over the past few months, I've switched a few decently-sized python codebases from MyPy (which I used for years) to PyreFly (because the MyPy LSP ecosystem is somewhere between crumbling and deprecated at this point), and finally to Ty after it left beta this week. I'm now running a fully Astral-ized (rust-ized!) setup:
1. packaging with uv (instead of pip or poetry),
2. type checking with ty (instead of the default MyPy or Meta's Pyrefly),
3. linting with ruff (instead of Jedi),
4. building with uv build (instead of the default setuptools or poetry build),
5. and publishing with uv publish (instead of the default twine)
...and I'm just here to just say that I highly recommend it!
Obviously obsessing over type checking libraries can quickly become bikeshedding for the typical project, but I think the cohesive setup ends up adding a surprising amount of value. That goes double if you're running containers.[1]
TBH I see Astral and Pydantic as a league of their own in terms of advancing Python, for one simple reason: I can trust them to almost always make opiniated decisions that I agree with. The FastApi/SQLModel guy is close, but there's still some headscratchers -- not the case with the former two. Whether it's docs, source code, or the actual interfaces, I feel like I'm in good hands.
TL;DR: This newly-minted fanboy recommends you try out ty w/ uv & ruff!
[1]https://docs.astral.sh/uv/guides/integration/docker/#availab...
The tagline: An extremely fast Python type checker, written in Rust.
@dang or another mod, can you add that to the title? Thanks!