Just a fast type checker and language server for Python, written in Rust.

Joined August 2026
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…
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🐍 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…
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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
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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.
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⚡ 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
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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
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