039类和对象：拾遗

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)#实例化放到一个新类里，就组合进去了
        self.fish = Fish(y)

    def print_num(self):
        print("水池里哟乌龟%d只。鱼%d条" % (self.turtle.num,self.fish.num))

            

mix-in