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Accepted
Мистер Фикс
Asked:2022-01-11 19:41:32 +0000 UTC2022-01-11 19:41:32 +0000 UTC

Python 类型提示。如何指定对象的类型？

  • 772
from abc import ABCMeta, abstractmethod


class AbstractObject(metaclass=ABCMeta):
    pass


class BObject(AbstractObject):
    pass


class CObject(AbstractObject):
    pass


class A(metaclass=ABCMeta):
    def restore_object(self) -> "AbstractObject":
        a = self.create_object()
        # другие действия
        return a

    @abstractmethod
    def create_object(self) -> "AbstractObject":
        pass


class B(A):

    def create_object(self):
        return BObject()


class C(A):

    def create_object(self):
        return CObject()


b_manager = B()
c_manager = C()

one_object: "BObject" = b_manager.restore_object()  # здесь ошибка типа
two_object: "CObject" = c_manager.restore_object()  # Expected type 'BObject', got 'AbstractObject' instead

调用方法“restore_object”时，无法指定所需的类型。在其他一些语言中，可以使用与我指出的大致相同的语法从抽象中细化返回类型。如何在 Python 中解决这个问题？

python

2 个回答

  1. Best Answer

    可以使类A 通用（如果您使用的是 Python 3.5 或更高版本）：

    from typing import TypeVar, Generic

...

T = TypeVar('T', bound=AbstractObject)


class A(Generic[T]):
    def restore_object(self) -> T:
        a = self.create_object()
        # другие действия
        return a

    @abstractmethod
    def create_object(self) -> T:
        pass


class B(A[BObject]):

    def create_object(self):
        return BObject()


class C(A[CObject]):

    def create_object(self):
        return CObject()


b_manager = B()
c_manager = C()

one_object: "BObject" = b_manager.restore_object()
two_object: "CObject" = c_manager.restore_object()
    • 4

  2. 试试这样：

    class AbstractObject(metaclass=ABCMeta):
    pass


class A(metaclass=ABCMeta):
    def restore_object(self) -> AbstractObject:
        a = self.create_object()
        # другие действия
        return a

    左右，如果预期以前未知的类型：

    from typing import Any

class A(metaclass=ABCMeta):
    def restore_object(self) -> Any:
        a = self.create_object()
        # другие действия
        return a
    • 2

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