>>>a=10
>>>b=10
>>>print(a is b)
True
>>>print(a is not b)
False
>>>b=20
>>>print(a is b)
False
>>>print(a is not b)
True
#is，判断两个标识符是否引用自同一个对象，  a is b  (10=10),那么 is 返回的结果就是1(True,真命题)
#is not，判断两个标识符是否引用自不同对象，a is not b (10≠10),那么is返回的结果1(False,假命题)

 end