Python type hints

[RussTedrake]

A number of users have requested that our python bindings/code use Python type hints. I'm opening this feature request to track it.

Related to #18452. I hear this often in feedback from students.

Tagging @EricCousineau-TRI as component owner.

[jwnimmer-tri]

To my understanding, the *.pyi files that we install already have this. Here's a pyi snippet from symbolic.pyi:

class Expression:
    @overload
    def __init__(self) -> None: ...
    @overload
    def __init__(self, constant: float) -> None: ...
    @overload
    def __init__(self, var: Variable) -> None: ...

Could you more precisely clarify what isn't working?

[jwnimmer-tri]

Maybe the request is that the small handful of public code that is pure Python (e.g., VideoWriter) add the type hints?

[RussTedrake]

I've asked @buoyancy99 to weigh in. He was one of the most vocal advocates.

[RussTedrake]

I talked to @buoyancy99 f2f and he said the solution that's already in place is great! Sorry I didn't realize it. Based on the original intention, I will close this (but I agree it could be good to add the type hints to our python code, so please re-open if you wish to track that).