Just a fast type checker and language server for Python, written in Rust.
Joined August 2026
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Pyrefly retweeted
Pyrefly support for tensor shape checking is here! Using simple type annotations, Pyrefly can catch tricky bugs in your models. Validated on dozens of real-world models including nanoGPT. Works with PyTorch, JAX, NumPy and more!
youtu.be/2dABb24Q-v0?is=UG3n…
If you've ever struggled with shape bugs in PyTorch, NumPy or JAX you can use Pyrefly shape checking to catch mismatches statically, before you ever run your code:
youtube.com/watch?v=2dABb24Q…
#pyrefly #python #pytorch #numpy
🐍 Come find our Meta booth at @PyConTW! 👋 Our team is here to talk about: 🔥 Pyrefly, 🧵 Free-threaded Python, 🛟 Safer Lazy Imports, and More! #pycontw #pycontw2026 #Python #OpenSource #Pyrefly #FreeThreading
The Pyrefly team wants to hear from you!
If you'd like to help make Pyrefly better and have a spare 10 mins to fill out this survey we would greatly appreciate it - whether you’re just getting started trying out Pyrefly or you’ve been here since the beginning:
📝 forms.gle/1ytEGVpsqokm7npR8
Pyrefly retweeted
🐍 Python 3.15 is here! One feature worth trying is explicit lazy imports.
They let you defer loading a module until your code actually uses it. For applications with costly imports, that can mean a much faster startup thanks to the use of built-in Python syntax.
Lazy imports arrived in PyCharm 2026.2 and will be enhanced further in 2026.3. Try them in the 2026.3 EAP now.
Curious how they work? Cheuk walks you through the feature and benchmarks it in our blog post: blog.jetbrains.com/pycharm/2…
ALT Python 3.15 is here!
Pyrefly retweeted
Read how our Python team transitioned from a homegrown checker to collaborating with the Pyrefly community on shared open-source infrastructure: goo.gle/pyrefly-at-google
Pyrefly retweeted
The best open source tool for the job doesn't have to be built in-house. When evaluating Python type checkers, Google chose @MetaOpenSource's Pyrefly and started contributing upstream. 👇 Link in first reply
Pyrefly retweeted
Tried @pyrefly_dev from @Meta on a 135k-line scientific Python codebase: 637,003 lines checked in 0.50s, vs 22.3s cold before. All 149 findings were accurate.
Adopting it in CI. Thanks to the Meta team we met at @py_bay: Kyle Into, Steven Troxler, @__avik and Martin DeMello.
🐍 We're at @py_bay ! Come find the Meta booth and say hi 👋 Our team is here to talk about: 🔥 Pyrefly, 🧵 Free-threaded Python, 🛟 Safer Lazy Imports, and More!
#PyBay2026 #Python #OpenSource #Pyrefly #FreeThreading
Python 3.15 is scheduled for tomorrow. Highlights include lazy imports, frozendict, sentinel, and new profiling tools.
Which feature are you trying first?
docs.python.org/3.15/whatsne…
JetBrains Air’s thesis: as agents generate more code, the bottleneck moves to verification and ownership.
"The agent said it was done" is not a quality gate. Put deterministic checks in the loop.
@pycharm congrats on the launch!
blog.jetbrains.com/blog/2026…
Napari migrated to Pyrefly and reduced type check times from 15s to <1s! Read their post for details 👇
Just published my first blog! 🥳
I wrote about my open-source journey and how we migrated from `mypy` to `pyrefly` in @napari_imaging
napari.org/island-dispatch/b…
Hope it helps if you're planning a similar migration!
#OpenSource #Python #Typing #Pyrefly #Mypy
Congrats on the #Jev launch, @typesafeai 🎉
We dug into the #Python adapter and were delighted to find Pyrefly running in strict mode across the source and tests.
Typed decisions 🤝 strictly typed client code. Typers unite.
github.com/typesafe-ai/syste…
Pyrefly retweeted
⚡ Waiting on type checks across massive, complex Python codebases?
Switch your type provider to Rust-based Pyrefly engine for near-instant diagnostic reports, precise error highlighting, and responsive inlay hints.
See what else is new in PyCharm 2026.2 ✌️ jb.gg/pq23i3
Pyrefly 1.3 is out: better control over errors, experimental tensor-shape checking for JAX/NumPy/PyTorch, and DataFrame schemas for Polars.
Python has always had shapes and schemas. Now they can stop living in comments and prayers.
pyrefly.org/blog/v1.3/
Pyrefly 1.3 is out: 934 commits, 71 contributors, and 88 bug fixes. The changelog brought snacks and stayed awhile.
Better framework support, smarter editor tools, faster analysis, plus experimental JAX and NumPy shape checking.
github.com/facebook/pyrefly/…
Pyrefly retweeted
Ever wondered why type systems don't automatically track tensor shapes across your neural network modules?
In his upcoming talk at PyTorch Conference North America 2026 (October 20–21 in San Jose, CA), Avik Chaudhuri from @Meta breaks down how PyreFly - a static type checker for Python - enables end-to-end static shape coverage for PyTorch models.
Register for PyTorchCon North America today: bit.ly/4qStJvL
#PyTorchCon @__avik
OpenAI’s research org now uses 3.1 agent-workdays per human workday.
Hopefully, that comes with 3.1× as many type checks.
openai.com/index/research-ac…
In 2023, the Python Typing Council was formed.
In 2026, the Python Packaging Council holds its inaugural elections (for eligible PSF voters) through September 15.
What Python Council will be next?
pyfound.blogspot.com/2026/09…
