#!/usr/bin/env python

 #抽象方法抽象类

 import abc

 class Foo(metaclass=abc.ABCMeta):

     def f1(self):

         raise Exception(".....")

     def f2(self):

         pass

     @abc.abstractmethod

     def f3(self):

         pass

 class Bar(Foo):

     def f1(self):

         print("....")

     def f3(self):#f3必须有

         print("...")