Several libraries let you declare objects with type-hinted members and automatically derive validation rules and serialization/deserialization from the type hints – Pydantic is the most popular, but alternatives like msgspec are out there too. There’s also a whole new generation of web frameworks like FastAPI and Starlite which use type hints at runtime to do not just input validation and serialization/deserialization but also things like dependency injection.
Personally, I’ve seen more significant gains in productivity from those runtime usages of Python’s type hints than from any static ahead-of-time type checking, which mostly is only useful to me as documentation.