Python 使用用户定义的类键入提示
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Type hints with user defined classes
提问by hhprogram
Couldn't seem to find a definitive answer. I want to do a type hint for a function and the type being some custom class that I have defined, called it CustomClass().
似乎找不到确切的答案。我想为一个函数做一个类型提示，类型是我定义的一些自定义类，称为它CustomClass()。
And then let's say in some function, call it FuncA(arg), I have one argument named arg. Would the correct way to type hint FuncAbe:
然后让我们说在某个函数中，调用它FuncA(arg)，我有一个名为 的参数arg。键入提示的正确方法FuncA是：
def FuncA(arg: CustomClass):
def FuncA(arg: CustomClass):
Or would it be:
或者它会是：
def FuncA(Arg:Type[CustomClass]):?
def FuncA(Arg:Type[CustomClass]):?
回答by Willem Van Onsem
The former is correct, if argaccepts an instance of CustomClass:
该前者是正确的，如果arg接受一个实例CustomClass：
def FuncA(arg: CustomClass):
# ^ instance of CustomClass
In case you want the class CustomClassitself (or a subtype), then you should write:
如果您想要类CustomClass本身（或子类型），那么您应该编写：
from typing import Type # you have to import Type
def FuncA(arg: Type[CustomClass]):
# ^ CustomClass (class object) itself
Like it is written in the documentation about Typing:
就像它写在关于Typing的文档中一样：
class typing.Type(Generic[CT_co])A variable annotated with
Cmay accept a value of typeC. In contrast, a variable annotated withType[C]may accept values that are classes themselves- specifically, it will accept the class object ofC.
class typing.Type(Generic[CT_co])带有注释的变量
C可以接受类型为 的值C。相比之下，用注释Type[C]的变量可能接受类本身的值- 具体来说，它将接受 的类对象C。
The documentation includes an example with the intclass:
该文档包括一个int类示例：
a = 3 # Has type 'int' b = int # Has type 'Type[int]' c = type(a) # Also has type 'Type[int]'
a = 3 # Has type 'int' b = int # Has type 'Type[int]' c = type(a) # Also has type 'Type[int]'
