類型提示以返回類型為參數的 function

Question

有沒有辦法輸入一個 function 作為參數的返回類型？ 我天真地嘗試這樣做：

# NOTE:
# This code does not work!
#
# If I define `ret_type = TypeVar("ret_type")` it becomes syntactically 
# correct, but type hinting is still broken.
#
def mycoerce(data: Any, ret_type: type) -> ret_type
    return ret_type(data)

a = mycoerce("123", int)  # desired: a type hinted to int
b = mycoerce("123", float)  # desired: b type hinted to float

但它不起作用。

Answer 1

看看Generics ，尤其是TypeVar 。 你可以這樣做：

from typing import TypeVar, Any

T = TypeVar("T")

def mycoerce(data: Any, ret_type: T) -> T:
    return ret_type(data)

a = mycoerce("123", int)  # desired: a type hinted to int
b = mycoerce("123", float)  # desired: b type hinted to float

print(a, b)