实例化抽象类时没有错误，即使没有实现抽象方法 [英] No error while instantiating abstract class, even though abstract method is not implemented

问题描述

我正在尝试以下 python 代码:

I was trying out the below python code:

from abc import ABCMeta, abstractmethod

class Bar:

    __metaclass__ = ABCMeta

    @abstractmethod
    def foo(self):
        pass


class Bar2(Bar):
    def foo2(self):
        print("Foo2")


b = Bar()
b2 = Bar2()

我认为拥有 @abstractmethod 将确保我的父类是抽象的，子类也将是抽象的，因为它没有实现抽象方法.但是在这里，尝试实例化这两个类都没有错误.

I thought having @abstractmethod will ensure that my parent class will be abstract and the child class would also be abstract as it is not implementing the abstract method. But here, I get no error trying to instantiate both the classes.

谁能解释一下为什么?

推荐答案

您必须将 Bar 类的 meta-class 设置为 ABCMeta.

You must set meta-class of Bar class to ABCMeta.

Python 2:

class Bar:
    __metaclass__ = ABCMeta

    @abstractmethod
    def foo(self):
        pass

Python 3:

class Bar(object, metaclass=ABCMeta):
    @abstractmethod
    def foo(self):
        pass

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