花点时间把python入门＜四十＞——多继承Mixlin

继承关系
子类单一的从父类继承

1.class animal(object):
    pass
#大类
class mammal(animal):
    pass
class bird(animal):
    pass
#各种动物
class dog(mammal):
    pass
class ostrich(bird):
    pass

子类继承多个父类，即多继承Mixlin

class runnable(object):
    pass
class flyable(object):
    pass
class dog(animal,runnable):
    pass
class ostrich(bird,flyable):
    pass