python 抽象类

这是一个正常类

#!/usr/bin/env python
# -*- encoding: utf-8 -*-
class A:
    def f(self):
        pass


class B(A):
    def g(self):
        print("g")


if __name__ == "__main__":
    a = A()
    b = B()
    b.g()  # g
    b.f()

抽象类（C++中含有纯虚函数的类，）
让A继承ABC，然后给f标上@abstractmethod，A就是一个抽象类了
必须要实现f才能实例化

#!/usr/bin/env python
# -*- encoding: utf-8 -*-
from abc import ABC, abstractmethod


class A(ABC):
    @abstractmethod
    def f(self):
        pass


class B(A):
    def f(self):
        print("f")

    def g(self):
        print("g")


class C(A):
    pass


if __name__ == "__main__":
    # a = A()
    b = B()
    b.g()  # g
    b.f()  # f
    c = C()  # TypeError: Can't instantiate abstract class C with abstract methods f