Google Replaces Pytype with Meta's Pyrefly for Python Type Checking

Google has switched from its own Pytype to Pyrefly, an open-source type checker originally developed by Meta. Internal benchmarks show Pyrefly is about 10x faster, cuts incremental rebuild latency by up to 98% and reduces peak compute cost by over 80%.

• Pyrefly is about 10x faster than Pytype in Google's benchmarks
• Incremental rebuild latency reduced by up to 98%
• Peak compute cost for type checking cut by over 80%
• Pyrefly passes roughly 97% of the Python typing conformance suite