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Comment by Handprint4469 | Hacker News Reader

If you have uv installed, you can test it without installing by running:

  uvx ty check

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Here's what I got against one of my larger open source projects:

  cd /tmp
  git clone https://github.com/simonw/sqlite-utils
  cd sqlite-utils
  uvx ty check

Here's the output: https://gist.github.com/simonw/a13e1720b03e23783ae668eca7f6f...

Adding "time uvx ty check" shows it took:

  uvx ty check  0.18s user 0.07s system 228% cpu 0.109 total

how does it compare against mypy? is it much faster?

How does it compare against Pyright. Pyright is the gold standard of Python type checking currently. Mypy is slower and buggier.

Mypy is also able to check things that are inexpressible with stubs, among other things

0.2s on ty compared to 4.7s on pyright. Not even close.

I tested it side-by-side on my ~100Kloc codebase.

Ty: 2.5 seconds, 1599 diagnostics, almost all of which are false positives

Pyright: 13.6 seconds, 10 errors, all of which are actually real errors

There's plenty of potential here, but Ty's type inference is just not as sophisticated as Pyright's at this time. That's not surprising given it hasn't even been released yet.

Whether Ty will still perform so much faster once all of Pyright's type inference abilities have been matched or implemented - well, that remains to be seen.

Pyright runs on Node, so I would expect it to be a little slower than Ty, but perhaps not by very much, since modern JS engines are already quite fast and perform within a factor of ~2-3x of Rust. That said, I'm rooting for Ty here, since even a 2-3x performance boost would be useful.

In the same folder:

    time uvx mypy .

Result:

    uvx mypy .  0.46s user 0.09s system 74% cpu 0.740 total

So ty is about 7x faster - but remember ty is still in development and may not catch the same errors / report false errors, so it's not a fair comparison yet.

Note that `uvx mypy` may give you inaccurate timings on macOS. The antivirus in macOS goes a little crazy the first time it executes a mypyc compiled program.

I'm not sure if it's using your environment correctly, or are you expecting ~150 errors? Lots of import errors, and I'm guessing most of the other ones are errors because it couldn't infer what was imported.

You can also install it "globally" for your user with:

  uv tool install ty

Then you can use it anywhere

  ty check

Can also do

   uv tool run ty

If your $PATH sucks

Found 275 diagnostics

0.56s user 0.14s system 302% cpu 0.231 total

Damn that's fast. And zero issues in this project with pyright so curious that these are...

There's a good chance many of the errors we emit are incorrect, at this stage. Lots to do still!

Wait wait wait

Carl, you did not tell me that the errors we emit need to be correct!!

I think I need to go revisit some of my PRs...

I knew we left something important out of that onboarding document

Why don't you just run ty on the ty codebase and let it tell you which errors are correct and which are erroneous?

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