Python：类的组合

class Turtle:    def __init__(self,x):        self.num=xclass Fish:    def __init__(self,x):        self.num=xclass Pool:    def __init__(self,x,y):        self.turtle=Turtle(x)        self.fish=Fish(y)    def print_num(self):        print('水池里总共有乌龟%d只，小鱼%d条'%(self.turtle.num,self.fish.num))pool=Pool(1,10)print(pool.print_num())