3. 成员运算符和身份运算符

一：成员运算符

1. in

• 判断一个字符或者字符串是否存在于一个大字符串中

print("eogn" in "hello eogn")
print("e" in "hello eogn")

True
True

• 判断元素是否存在于列表

print(1 in [1,2,3])
print('x' in ['x','y','z'])

True
True

• 判断key是否存在于字典

print('k1' in {'k1':111,'k2':222})
print(111 in {'k1':111,'k2':222})

True
False

2. not in

• 判断一个字符或者字符串是否存在于一个大字符串中

print("eogn" not in "hello eogn")
print("e" not in "hello eogn")

False
False

• 判断元素是否存在于列表

print(1 not in [1,2,3])
print('x' not in ['x','y','z'])

False
False

• 判断key是否存在于字典

print('k1' not in {'k1':111,'k2':222})
print(111 not in {'k1':111,'k2':222})

False
True

二：身份运算符

1. is

• 判断的是id是否相等

• 如果引用的是同一个对象则返回 True，否则返回 False

x = 1
y = 1
print(x is y)

True
x = 1
y = 2
print(x is y)

False

2. not is

• 是判断两个标识符是不是引用自不同对象

• 如果引用的不是同一个对象则返回结果 True，否则返回 False

x = 1
y = 1
print(x is not y)

False
x = 1
y = 2
print(x is not y)

True

三：短路运算

偷懒原则，偷懒到哪个位置，就把当前位置的值返回

10>3 and 10 and None and 10 //返回None

10>3 and 10 and None and 10 or 10 > 3 and 1 == 1 //返回True