如何注释以另一个函数为参数的函数？

Question

I'm experimenting with type annotations in Python. Most cases are pretty clear, except for those functions that take another function as parameter.

Consider the following example:

from __future__ import annotations

def func_a(p:int) -> int:
    return p*5
    
def func_b(func) -> int: # How annotate this?
    return func(3)
    
if __name__ == "__main__":
    print(func_b(func_a))

The output simply prints 15 .

How should I annotate the func parameter in func_b( ) ?

Answer 1

You can use the typing module for Callable annotations.

The Callable annotation is supplied a list of argument types and a return type:

from typing import Callable

def func_b(func: Callable[[int], int]) -> int:
    return func(3)

Answer 2

Shouldn't it just be function ?

>>> type(func_a)
function