​​Beartype is an open-source pure #python PEP-compliant O(1) constant-time runtime type checker emphasizing efficiency, portability, and thrilling puns.

Beartype brings Rust inspired zero-cost abstractions into the lawless world of dynamically-typed pure Python.

Beartype is portably implemented in Python 3, continuously stress-tested via GitHub Actions + tox + pytest, and permissively distributed under the MIT license. Beartype has no runtime dependencies, only one test-time dependency, and supports all Python 3.x releases still in active development.

https://github.com/beartype/beartype