如何键入带有封闭 class 类型的方法并使用 inheritance 更新该方法？

Question

Similar but different to How do I type hint a method with the type of the enclosing class? .

How can I set something on the parent class so that a type hint gets updated through inheritance?

class A:
    # Make some change here
    def foo(self, bar: 'A'):
        pass


class B(A):
    # Get the hinting of the code below, but without writing it for every inheritor.
    # def foo(self, bar: 'B'):
    #     pass
    pass

Answer 1

Parameterise over the type of self , which is always an instance of "the current class":

from typing import TypeVar

Self = TypeVar('Self')

class A:
    # `bar` must be of the same type as the current instance `self`
    def foo(self: Self, bar: Self):
        pass


class B(A):
    pass

When calling A().foo or B().foo , Self is automatically inferred to the concrete class A or B , respectively. This then automatically constraints the other parameter to match the inferred TypeVar and thus the class.