python - 使用用户定义的类键入提示

Question

似乎找不到明确的答案。我想为一个函数做一个类型提示，该类型是我定义的一些自定义类，称为 CustomClass()。

然后假设在某个函数中，将其称为 FuncA(arg)，我有一个名为 arg 的参数。输入提示 FuncA 的正确方法是:

def FuncA(arg: CustomClass):

还是这样:

from typing import Type

def FuncA(Arg:Type[CustomClass]):

Answer 1

前者是正确的，如果 arg 接受 CustomClass 的实例:

def FuncA(arg: CustomClass):
    #     ^ instance of CustomClass

如果你想要类CustomClass本身(或子类型)，那么你应该写:

from typing import Type  # you have to import Type

def FuncA(arg: Type[CustomClass]):
    #     ^ CustomClass (class object) itself

就像在关于 Typing 的文档中所写的那样:

<b>class typing.Type(Generic[CT_co])</b>

A variable annotated with C may accept a value of type C. In contrast, a variable annotated with Type[C] may accept values that are classes themselves - specifically, it will accept the class object of C.

文档包含一个带有 int 类的示例:

a = 3         # Has type 'int'
b = int       # Has type 'Type[int]'
c = type(a)   # Also has type 'Type[int]'