以下代码的输出结果是什么? 产生此结果的原因是什么？ class An...

Question

以下代码的输出结果是什么? 产生此结果的原因是什么？

class Animal(object): 
    weight = 9
class Dog(Animal): 
    pass
class Cat(Animal): 
    pass
 
print Animal.weight, Dog.weight, Cat.weight
Cat.weight = 8
print Animal.weight, Dog.weight, Cat.weight
Animal.weight = 7
print Animal.weight, Dog.weight, Cat.weight