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A faster Python type checker written in Rust

$ pip install pyrefly && pyrefly init
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  • Scale with Confidence

    Type check over 1.85 million lines of code per second.ⓘTested using Meta infrastructure (166 cores, 228 GB RAM)

    Developer Delight

    Get lightning fast autocomplete, and catch errors with instant feedback in your favorite editor.

    Easy Onboarding

    Start type checking your code in minutes.

  • Performance Comparison

    Type checking the PyTorch codebase from scratch.ⓘTested using Macbook
    (10 cores: 8 performance + 2 efficiency cores, 32 GB RAM)
    PyreflyⓘCommand: "pyrefly check"
    Pyrefly uses as many threads as possible
    0.0s
    PyrightⓘCommand: "pyright --threads=8"
    8 threads yielded the best performance after testing multiple settings
    0.0s
    MyPyⓘCommand: "dmypy run"
    0.0s