How can I specify the function type in my type hints?

As @jonrsharpe noted in a comment, this can be done with typing.Callable:

from typing import Callable

def my_function(func: Callable):

Note: Callable on its own is equivalent to Callable[..., Any].
Such a Callable takes any number and type of arguments (...) and returns a value of any type (Any). If this is too unconstrained, one may also specify the types of the input argument list and return type.

For example, given:

def sum(a: int, b: int) -> int: return a+b

The corresponding annotation is:

Callable[[int, int], int]

That is, the parameters are sub-scripted in the outer subscription with the return type as the second element in the outer subscription. In general:

Callable[[ParamType1, ParamType2, .., ParamTypeN], ReturnType]

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