python中的抽象方法

import abc


class A(metaclass=abc.ABCMeta):
    @abc.abstractclassmethod
    def read(self):
        pass

    @abc.abstractclassmethod
    def write(self):
        pass


class B(A):
    def read(self):
        print("I am read")

    def write(self):
        print("I am write")


b = B()
b.read()
b.write()