您可以使用 mypy 将函数的类型定义为 python 中的参数吗？

Question

I'm trying to annotate and define my types in python 2.7 using mypy. I can't seem to find any documentation describing how one might pass a function as an argument and record its type. For example, in Scala I can define a function type which maps two ints to a boolean as:

def exampleFunction(f: (Int,Int) => Boolean) = {
  // Do Something
}

Is there similar notation in mypy? Something like this perhaps?

def exampleFunction(f):
    # type: ((int, int) -> bool) -> None
    # Do Something

What is the best practice for annotating function types when they are arguments?

Answer 1

For anyone stumbling upon this question when googling how to give a type to a function (in Python 3, havent tested for 2), this could be useful:

In principle, the syntax is Callable[[<parameters>], <return type>]

Some examples, for the 3 possible types of functions

1. function f with parameters and return
2. function g with only return
3. function h with only parameters

I made 3 check-functions, that take the function as input. I want to illustrate what type to give to a parameter if this parameter is a function.

from typing import Callable


    def f(i: int) -> bool:
        return i > 0

    def g() -> bool:
        return True

    def h(i: int, j: int):
        pass

    def check_f(function: Callable[[int], bool]):
        print(function(1))

    def check_g(function: Callable[[], bool]):
        print(function())

    def check_h(function: Callable[[int, int], None]):
        print(function(1, 1))

    check_f(f)
    check_g(g)
    check_h(h)

prints

True
True
None

Mypy says: Success: no issues found in 1 source file