Suggesting pyrefly as a type-checking alternative to mypy

[camilotabaresj]

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Example Code

Example using pyrefly for fast type checking in a large-scale project
The `pyrefly check` command is much faster than `mypy` in large codebases

# Install pyrefly:

pip install pyrefly && pyrefly init


Run type check with pyrefly in backend folder
```python
pyrefly check app

Description

I have a large-scale project, and over time, the mypy type checking started to take significantly longer as the codebase expanded. To address this issue, I switched to pyrefly, a type checker written in Rust by Meta's team, which offers substantial performance improvements and full integration with typing. It's notably faster, especially when working with large projects, and provides a more responsive experience overall.

I would like to propose pyrefly as an alternative to mypy for type checking in codebases. It's faster, more efficient, and better suited for projects where mypy may struggle with performance due to their size. I believe this could help improve type-checking workflows, particularly for teams working on large repositories.

The image above presents a side-by-side comparison of type-checking performance between mypy and pyrefly on the full PyTorch codebase.

I have full disposition to implement this, obviously if the community agrees

Operating System

Linux

Operating System Details

Ubuntu 24

Python Version

Python 3.12.3

Additional Context

No response