继承

import random as r
class Fish:
    def __init__(self):
        self.x = r.randint(0,10)
        self.y = r.randint(0,10)

    def move(self):
        self.x -= 1
        print('我的位置上: ',self.x,self.y)
class Goldfish(Fish):
    pass
class Carp(Fish):
    pass
class Salmon(Fish):
    pass
class Shark(Fish):
    def __init__(self):
        super().__init__()#若不加, 则__init__被替换,Shark.move 无法调用 
        #Fish.__init__(self)
        self.hungry = True
    def eat(self):
        if self.hungry:
            print('吃货的梦想就是天天吃')
            self.hungry = False
        else:
            print('吃不下了')

多重继承

组合

class Turtle:
    def __init__(self,x):
        self.num=x


class Fish:
    def __init__(self,x):
        self.num=x

class Pool:
    def __init__(self,x,y):
        self.turtle = Turtle(x)
        self.fish = Fish(y)

    def print_num(self):
        print('水池里有乌龟 %d 只,鱼 %d 条'%(self.turtle.num,self.fish.num))