dog.py

class Dog2:
    kind = 'canine'  # class variable shared by all instances

    def __init__(self, name):
        self.name = name  # instance variable unique to each instance


dogX = Dog2("Yanan")
dogY = Dog2("Anan")

print("-=CLASS VARIABLE=-") # 这个kind是保存在class里的

print("Dog2.kind: " + Dog2.kind)

print("-=INSTANCES=-")

print("dogX.name: " + dogX.name) # name是每个instance都会各自保存的
print("dogY.name: " + dogY.name)
print("dogX.kind: " + dogX.kind) # 实际是class variable，所以从instance里面取出来也是class里面的
print("dogY.kind: " + dogY.kind)

print("-=RESET CLASS VARIABLE=-")
Dog2.kind = "hahaha" # 因为是class variable，所以改动以后，各个instances查看的时候也就跟着变了，因为实际只有class里面保存一份

print("dog2.kind(): " + Dog2.kind)
print("dogX.kind(): " + dogX.kind)
print("dogY.kind(): " + dogY.kind)