Meta’s Pyrefly revolutionizes Python development with real-time type checking that analyzes 1.8 million lines per second. This Rust-based type checker and language server handles massive codebases effortlessly, offering instant feedback, smart navigation, and seamless IDE integration for data scientists and engineers alike.
Key Features for Modern Python Workflows
- Real-time autocomplete and go-to-definition across million-line projects
- Advanced type inference for unannotated code and return values
- Flow-aware narrowing for precise logic-based type refinement
- Automatic import updates during refactoring
- Built-in stubs for Django, Pydantic, and popular libraries
Blazing Performance and Scalability
Pyrefly delivers 95% faster type checking than Meta’s previous tools, processing Instagram’s entire codebase in 13 seconds. Incremental checking updates only changed modules, maintaining speed in collaborative environments without full reanalysis.
Seamless IDE Integration
Production-ready extensions work flawlessly with VS Code, PyCharm, and NeoVim:
- Instant hover information and error diagnostics
- Smart error messages with actionable fixes
- Precise dependency tracking across complex projects
- Jupyter notebook support for data workflows
Easy Migration from MyPy/Pyright
Pyrefly auto-generates config files from existing tools, supports gradual adoption with baselines, and preserves suppressed errors and include/exclude rules for smooth transitions.
Beta Status and Roadmap
Now at 70% Python typing spec compliance (up from 39% alpha), Pyrefly fixed 350+ bugs. Future updates target full spec support, deeper library coverage, lower memory use, and faster incremental checks for v1 stable release.
