用抽象基类暗示Python类型[重复]

Question

我有一个ABC方法，子类应该返回它们自己的类型，我正在尝试找出最好的方式来类型提示这个方法。例如：

from abc import ABC, abstractmethod

class Base(ABC):
    @abstractmethod
    def f(self): ## here i want a type hint for type(self)
        pass

class Blah(Base):
    def __init__(self, x: int):
        self.x = x

    def f(self) -> "Blah":
        return Blah(self.x + 1)

我能想到的最好的是这个，有点重：

from abc import ABC, abstractmethod
from typing import TypeVar, Generic

SELF = TypeVar["SELF"]

class Base(ABC, Generic[SELF]):

    @abstractmethod
    def f(self) -> SELF:
        pass

class Blah(Base["Blah"]):

    def __init__(self, x: int):
        self.x = x

    def f(self) -> "Blah":
        return Blah(self.x+1)

我有更好/更干净的方法吗？

Answer 1

使用Python3.7，它通过从\uuuuu future\uuuuu

from __future__ import annotations

class Base():
    def f(self) -> Base: ## Here the type is Base since we can not guarantee it is a Blah
        pass

class Blah(Base):
    def __init__(self, x: int):
        self.x = x

    def f(self) -> Blah: ## Here we can be more specific and say that it is a Blah
        return Blah(self.x + 1)