Python: typed method arguments

Question

In Python3, you can add a type to function arguments:

def foo(bar: str = "default") -> str:
    """
    @param bar: a textual value
    """
    return "test"

Now I have two questions. First, how can you do this for a callback function ? Sense, how to determine the signature of this callback in the function header?

def foo(callback) -> str:
    """
    @param callback: function(value: str) -> str
    """
    # calculate some intermediate stuff
    my_var = ...    
    return callback(my_var)

Secondly, how to do this for tuples . This will include determining that the value is of the tuple type and should have two values ​​(without a triple, etc.).

def foo(value) -> str:
    """
    @param value: tuple of strings
    """

    v1, v2 = value
    return v1 + v2

Thanks for your comments and answers.

Answer 1

To indicate the signature of your callback function, you can use Callable , for example:

from typing import Callable


def foo(callback: Callable[[str], str]) -> str:
    # calculate some intermediate stuff
    my_var = '...'
    return callback(my_var)

tuple :

from typing import Tuple


def foo(value: Tuple[str, str]) -> str:
    v1, v2 = value
    return v1 + v2