I'm a little worried on behalf of the "Python Language Tooling Team" at Meta, because uv has been so popular, and I wouldn't be surprised if ty wins out in this space.

So watch out, or this will become like Atom or Flow, an internal competitor of a technology that is surpassed by the more popular external open source version, leaving the directors/vps muttering to themselves "It's too bad that this team exists at all. Could we get rid of them and just switch to the open source stuff?"

Perhaps just something for the manager (Aaron Pollack?) to keep an eye on....

Hi folks, I work on the Pyrefly team at Meta. Our FAQ covers a good number of the questions raised here: https://pyrefly.org/en/docs/pyrefly-faq/. I can also try to answer some of your questions. Thanks for taking a look!

Seems there are at least three Rust-based competitors for type checkers in Python now (Microsoft, Facebook, Astral), and of course there's still mypy.

Why is "written in Rust" a feature to be mentioned? Who cares? So my type checker has memory protection and is compiled. I'm not running my type checker on an embedded system or in a mission critical service. It seems kind of like "written in Erlang". I'd prefer to have non-performance critical code for Python written in Python. That way the broader community can support and extend it.

I just tried pyrefly on a project that really needed it. It complained about an assignment of a new value to a global int variable within a function, even though the function contained the 'global' statement that should have made that OK, I think. I know that globals and assigning to them here and there are problematic for real good software, but I am surprised that Pyrefly is stricter than python on something that I don't see as a type- checking issue. But it did find a decent list of other problems that I haven't finished working my way through.

I had gotten so messed up trying to put together a quicky hobby-type program to create a data structure of perhaps a hundred data items in various overlapping and inter-related hierarchies, tuples, dicts, and lists akimbo, that I gave up on it about 10 days ago. I hypothecated that bondage and discipline might be the way to control the confusion, so I'm rewriting, using SQLite for the dataflow from function to function, lots of little tables and no optional fields. Can anyone opine on whether that is a sensible option?