I have a Python function with an overloaded signature, for example float → float, str → int. I would like it to have it typed correctly, using annotations etc., so that mypy can check it correctly, and that tools like autocomplete will work. Is this possible? I appreciate different tools will have varying support, so mypy can be the standard for this question. I can use any released version of Python 3.
Yes, you can use the @typing.overload decorator.
From https://docs.python.org/3/library/typing.html#typing.overload:
@overload
def process(response: None) -> None:
...
@overload
def process(response: int) -> tuple[int, str]:
...
@overload
def process(response: bytes) -> str:
...
def process(response):
<actual implementation>
Those ellipses (...) are literal. You will actually type three dots for each overloaded function signature. The actual code will go in the final definition.