is与==

 is和==的区别

1. id()

　　通过id()我们可以查看到⼀一个变量表示的值在内存中的地址.

a1 = 100
b1 = 100
print(id(a1),id(b1))  #140712472404096, 140712472404096

a2 = 222222222222
b2 = 222222222222
print(id(a2),id(b2))  #2714854086672, 2714854086672

a3 = True
b3 = True
print(id(a3),id(b3))  #140712471869776, 140712471869776  内存地址相同

a4 = "abcdefghijklmnopqrstuvwxyz"
b4 = "abcdefghijklmnopqrstuvwxyz"
print(id(a4),id(b4))  #2230116006848, 2230116006848  内存地址相同

a5 = "abcdefghijklmnopqrstuvwxyz"*3
b5 = "abcdefghijklmnopqrstuvwxyz"*3
print(id(a5),id(b5))   #2234044245808, 2234044245808  内存地址相同

a6 = "uwidsoididoiwqoiewyueiydihbddwowqfewhufdnjcddududfisdygfiuwqiodmcdncduiosiiennxeniionwmwoiwieuruuewuuukskxsniiwhdhi2wuyrtfrvvufioqkq"*3
b6 = "uwidsoididoiwqoiewyueiydihbddwowqfewhufdnjcddududfisdygfiuwqiodmcdncduiosiiennxeniionwmwoiwieuruuewuuukskxsniiwhdhi2wuyrtfrvvufioqkq"*3
print(id(a6),id(b6))  #1998595213104, 1998595213104  内存地址相同

a7 =  ["hello""world"]
b7 =  ["hello""world"]
print(id(a7),id(b7))  #1915401364040, 1915401364104  内存地址不同


a8 = ("hello","world")
b8 = ("hello","world")
print(id(a8),id(b8))  #2328127912840, 2328127912840  内存地址相同

a9 = {"hello":"你好","world":"世界"}
b9 = {"hello":"你好","world":"世界"}
print(id(a9),id(b9))  #1975585307384, 1975585307456  内存地址不同

　　注意(一般情况下): 在py文件中. 如果你只是单纯的定义一个字符串. 那么一般情况下都是会被添加到小数据池中的. 我们可以这样认为: 在使⽤用字符串的时候, python会帮我们把字符串进行缓存, 在下次使用的时候直接指向这个字符串即可. 可以节省很多内存.

　　==: 判断两端的值是否相等

　　is: 判断两端的内存地址是否相等

a = "who am i"
b = "who am i"
print(id(a),id(b))  #2142885576880, 2142885576880
print(a is b)  #True
print(a == b)  #True


li1 = ["who","am","i"]
li2 = ["who","am","i"]
print(id(li1),id(li2)) #1891093340744, 1891093340808
print(li1 is li2)  #False
print(li1 == li2)  #True