成员运算符

• 成员运算符的作用是判断一个元素是否在另外一组元素中
• 成员运算符的作用返回的是bool

>>> a = 1
>>> a in [1,2,3,4,5]
True
>>> a in [2,3,4,5]
False
>>> b='h'
>>> b in "hello"
True
>>> b not in {1,2,3,4,5}
True

字典里验证的是key

>>> b = "a"
>>> b in {'c':1}
False
>>> b ='c'
>>> b in {'c':1} # b 表示的key
True