结果是值:
算术运算
a = 1 + 1
赋值运算
a+=1 a = a + 1
结果是布尔值:
比较运算
a = 1 > 5
逻辑运算
a = 1 > 5 or 1 == 1
成员运算
a = "您好" in "您好世界"