facebook/pyrefly
A fast type checker and language server for Python
Build with Backblaze B2
SDKs, agent skills, IDE extensions, and reference pipelines from Backblaze Labs. All open source.
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Where it stands
Rank, growth pace and release cadence relative to everything GStars tracks.
5 releases in the last 90 days, the latest 12 days ago, with 316 contributors on GitHub.
Peaked at #30 in the weekly ranking the week of Nov 30, its best in the past year.
Use Cases & Benefits
- Provides a fast type checker and language server for Python to improve code quality and IDE support.
- Delivers high performance and large-scale incremental type checking using Rust and module-level parallelism.
- Use for integrating efficient type checking and type inference into Python development workflows.
- Use for enhancing IDEs like VSCode with real-time Python type checking and language server features.
- Use for analyzing and refining Python codebases with complex control flow and type annotations.
Should you depend on it?
License terms, project hygiene and risks, from GitHub metadata and GStars' snapshots.
License
MIT
Permissive: commercial use, modification and redistribution are allowed with attribution.
Community files
- README: present
- Contributing guide: present
- Code of conduct: present
Watch-outs
No watch-outs from GStars' checks.
General guidance from repository metadata, not legal advice. How we score
From the README
Currently under active development with known issues. Please open an issue if you find bugs.
Pyrefly is a fast type checker for Python. It's designed to replace the existing Pyre type checker at Meta by the end of 2025. This README describes basic usage. See the Pyrefly website for full documentation and a tool for checking code.
Pyrefly aims to increase development velocity with IDE features and by checking your Python code.
Daily snapshots
Stars gained per day, and how forks and open issues moved, from GStars' daily snapshots
+313 stars over 87 days across 10 snapshot days; best day +4 on Aug 3.
Forks
578+113
Open issues
739+40
Compared with peers in Developer Tools
Fastest-growing repositories GStars tracks in this cohort for the week of Nov 1, by 7-day star growth
| Repository | Stars | +7d | Health | Last release |
|---|---|---|---|---|
| stablyai/orca | 116.8K | +6.6K | 40 | today |
| affaan-m/ECC | 297.9K | +5.2K | 63 | 35 days ago |
| DietrichGebert/ponytail | 185.3K | +5.1K | 60 | 7 days ago |
| herdrdev/herdr | 48.3K | +1.7K | 59 | 22 days ago |
| The-PR-Agent/pr-agent | 15.1K | +1.5K | 64 | 11 days ago |
| facebook/pyrefly | 7.2K | — | 64 | 12 days ago |
| Category median | 116.8K | +5.1K | 60 | — |
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