Python-in is == 区别

 

in

　　判断单个元素是否在序列中， 对字典来说只能判断key，在不在关系

print("ab" in "abcdefg")
print("abc" in ["abc", "ac"])
print([1, 2] in [[1, 2], "3"])
print("abc" in {"abc": 33})
print(33 in {"abc": 33})

 

is

　　身份判断，判断内存地址是否相等，是不是关系

nameOne = "BeiMenChuiXue"
nameTwo = "QiNiuYun"
nameThree = "QiNiuYun"

print(nameOne is nameTwo, id(nameOne), id(nameTwo))
print(nameTwo is nameThree, id(nameTwo), id(nameThree))

 

==

　　判断值是否相等，等不等关系

nameOne = "BeiMenChuiXue"
nameTwo = "QiNiuYun"
nameThree = "QiNiuYun"

print(nameOne == nameTwo)
print(nameTwo == nameThree)

　

相同点

　　in is == 返回都是bool类型 True 或 False

 

注意点

　　=赋值语句中，对于小段字符串，则直接引用而不是重新生成

name = "北门吹雪"
name_two = "北门吹雪"
print(name is name_two)