class Animal(object):
    def run(self):
        print('Animal is running')


class Dog(Animal):
    def run(self):
        print('dog is running')
    pass


class Cat(Animal):
    def run(self):
        print('cat is running')
    pass


dog = Dog()
dog.run()

cat = Cat()
cat.run()

# 判断是否是Dog类型
print(isinstance(dog, Dog))
# 判断是否是Animal类型
print(isinstance(dog, Animal))


def run_twice(animal):
    animal.run()
    animal.run()


run_twice(Animal())
run_twice(Dog())
run_twice(Cat())

# 动态语言只需要保证对象有一个run()函数,就能被执行
# 静态语言需要对象必须是某个父类的子类才行
# 动态语言的鸭子类型,"只要看起来像鸭子,走起路来像鸭子",那么它就可以被看做是鸭子