什么是运算符？
本章节主要说明python的运算符。举个简单的例子 4 +5 = 9 。 例子中，4和5被称为操作数，+号为运算符。
python语言支持以下类型的运算符:
算术运算符
比较（关系）运算符
赋值运算符
逻辑运算符
位运算符
成员运算符
身份运算符
运算符优先级
接下来让我们一个个来学习python的运算符。
python算术运算符
以下假设变量a为10，变量b为20：
运算符
描述
实例
+    加 - 两个对象相加    a + b 输出结果 30    
-    减 - 得到负数或是一个数减去另一个数    a - b 输出结果 -10    
*    乘 - 两个数相乘或是返回一个被重复若干次的字符串    a * b 输出结果 200    
/    除 - x除以y    b / a 输出结果 2    
%    取模 - 返回除法的余数    b % a 输出结果 0    
**    幂 - 返回x的y次幂    a**b 输出结果 20    
//    取整除 - 返回商的整数部分    9//2 输出结果 4 , 9.0//2.0 输出结果 4.0    
以下实例演示了python所有算术运算符的操作：
#!/usr/bin/python a = 21 b = 10 c = 0 c = a + b print "line 1 - value of c is ", c c = a - b print "line 2 - value of c is ", c c = a * b print "line 3 - value of c is ", c c = a / b print "line 4 - value of c is ", c c = a % b print "line 5 - value of c is ", c a = 2 b = 3 c = a**b print "line 6 - value of c is ", c a = 10 b = 5 c = a//b print "line 7 - value of c is ", c
以上实例输出结果：
line 1 - value of c is 31 line 2 - value of c is 11 line 3 - value of c is 210 line 4 - value of c is 2 line 5 - value of c is 1 line 6 - value of c is 8 line 7 - value of c is 2
python比较运算符
以下假设变量a为10，变量b为20：
运算符
描述
实例
== 等于 - 比较对象是否相等 (a == b) 返回 false。
!= 不等于 - 比较两个对象是否不相等 (a != b) 返回 true.
<> 不等于 - 比较两个对象是否不相等 (a <> b) 返回 true。这个运算符类似 != 。
> 大于 - 返回x是否大于y (a > b) 返回 false。
< 小于 - 返回x是否小于y。所有比较运算符返回1表示真，返回0表示假。这分别与特殊的变量true和false等价。注意，这些变量名的大写。 (a < b) 返回 true。
>= 大于等于 - 返回x是否大于等于y。 (a >= b) 返回 false。
<= 小于等于 - 返回x是否小于等于y。 (a <= b) 返回 true。
以下实例演示了python所有比较运算符的操作：
#!/usr/bin/python a = 21 b = 10 c = 0 if ( a == b ): print "line 1 - a is equal to b" else: print "line 1 - a is not equal to b" if ( a != b ): print "line 2 - a is not equal to b" else: print "line 2 - a is equal to b" if ( a <> b ): print "line 3 - a is not equal to b" else: print "line 3 - a is equal to b" if ( a < b ): print "line 4 - a is less than b" else: print "line 4 - a is not less than b" if ( a > b ): print "line 5 - a is greater than b" else: print "line 5 - a is not greater than b" a = 5; b = 20; if ( a <= b ): print "line 6 - a is either less than or equal to b" else: print "line 6 - a is neither less than nor equal to b" if ( b >= a ): print "line 7 - b is either greater than or equal to b" else: print "line 7 - b is neither greater than nor equal to b" 以上实例输出结果： line 1 - a is not equal to b line 2 - a is not equal to b line 3 - a is not equal to b line 4 - a is not less than b line 5 - a is greater than b line 6 - a is either less than or equal to b line 7 - b is either greater than or equal to b
python赋值运算符
以下假设变量a为10，变量b为20：
运算符
描述
实例
= 简单的赋值运算符 c = a + b 将 a + b 的运算结果赋值为 c
+= 加法赋值运算符 c += a 等效于 c = c + a
-= 减法赋值运算符 c -= a 等效于 c = c - a
*= 乘法赋值运算符 c *= a 等效于 c = c * a
/= 除法赋值运算符 c /= a 等效于 c = c / a
%= 取模赋值运算符 c %= a 等效于 c = c % a
**= 幂赋值运算符 c **= a 等效于 c = c ** a
//= 取整除赋值运算符 c //= a 等效于 c = c // a
以下实例演示了python所有赋值运算符的操作：
#!/usr/bin/python a = 21 b = 10 c = 0 c = a + b print "line 1 - value of c is ", c c += a print "line 2 - value of c is ", c c *= a print "line 3 - value of c is ", c c /= a print "line 4 - value of c is ", c c = 2 c %= a print "line 5 - value of c is ", c c **= a print "line 6 - value of c is ", c c //= a print "line 7 - value of c is ", c 以上实例输出结果： line 1 - value of c is 31 line 2 - value of c is 52 line 3 - value of c is 1092 line 4 - value of c is 52 line 5 - value of c is 2 line 6 - value of c is 2097152 line 7 - value of c is 99864
python位运算符
按位运算符是把数字看作二进制来进行计算的。python中的按位运算法则如下：
运算符
描述
实例
& 按位与运算符 (a & b) 输出结果 12 ，二进制解释： 0000 1100
| 按位或运算符 (a | b) 输出结果 61 ，二进制解释： 0011 1101
^ 按位异或运算符 (a ^ b) 输出结果 49 ，二进制解释： 0011 0001
~ 按位取反运算符 (~a ) 输出结果 -61 ，二进制解释： 1100 0011， 在一个有符号二进制数的补码形式。
<< 左移动运算符 a << 2 输出结果 240 ，二进制解释： 1111 0000
>> 右移动运算符 a >> 2 输出结果 15 ，二进制解释： 0000 1111
以下实例演示了python所有位运算符的操作：
#!/usr/bin/python a = 60 # 60 = 0011 1100 b = 13 # 13 = 0000 1101 c = 0 c = a & b; # 12 = 0000 1100 print "line 1 - value of c is ", c c = a | b; # 61 = 0011 1101 print "line 2 - value of c is ", c c = a ^ b; # 49 = 0011 0001 print "line 3 - value of c is ", c c = ~a; # -61 = 1100 0011 print "line 4 - value of c is ", c c = a << 2; # 240 = 1111 0000 print "line 5 - value of c is ", c c = a >> 2; # 15 = 0000 1111 print "line 6 - value of c is ", c
以上实例输出结果：
line 1 - value of c is 12
line 2 - value of c is 61
line 3 - value of c is 49
line 4 - value of c is -61
line 5 - value of c is 240
line 6 - value of c is 15
python逻辑运算符
python语言支持逻辑运算符，以下假设变量a为10，变量b为20：
运算符
描述
实例
and 布尔"与" - 如果x为false，x and y返回false，否则它返回y的计算值。 (a and b) 返回 true。
or 布尔"或" - 如果x是true，它返回true，否则它返回y的计算值。 (a or b) 返回 true。
not 布尔"非" - 如果x为true，返回false。如果x为false，它返回true。 not(a and b) 返回 false。
以下实例演示了python所有逻辑运算符的操作：
#!/usr/bin/python a = 10 b = 20 c = 0 if ( a and b ): print "line 1 - a and b are true" else: print "line 1 - either a is not true or b is not true" if ( a or b ): print "line 2 - either a is true or b is true or both are true" else: print "line 2 - neither a is true nor b is true" a = 0 if ( a and b ): print "line 3 - a and b are true" else: print "line 3 - either a is not true or b is not true" if ( a or b ): print "line 4 - either a is true or b is true or both are true" else: print "line 4 - neither a is true nor b is true" if not( a and b ): print "line 5 - a and b are true" else: print "line 5 - either a is not true or b is not true" 以上实例输出结果： line 1 - a and b are true line 2 - either a is true or b is true or both are true line 3 - either a is not true or b is not true line 4 - either a is true or b is true or both are true line 5 - a and b are true
python成员运算符
除了以上的一些运算符之外，python还支持成员运算符，测试实例中包含了一系列的成员，包括字符串，列表或元组。
运算符
描述
实例
in 如果在指定的序列中找到值返回true，否则返回false。 x 在 y序列中 , 如果x在y序列中返回true。
not in 如果在指定的序列中没有找到值返回true，否则返回false。 x 不在 y序列中 , 如果x不在y序列中返回true。
以下实例演示了python所有成员运算符的操作：
#!/usr/bin/python a = 10 b = 20 list = [1, 2, 3, 4, 5 ]; if ( a in list ): print "line 1 - a is available in the given list" else: print "line 1 - a is not available in the given list" if ( b not in list ): print "line 2 - b is not available in the given list" else: print "line 2 - b is available in the given list" a = 2 if ( a in list ): print "line 3 - a is available in the given list" else: print "line 3 - a is not available in the given list"
以上实例输出结果：
line 1 - a is not available in the given list
line 2 - b is not available in the given list
line 3 - a is available in the given list
python身份运算符
身份运算符用于比较两个对象的存储单元
运算符
描述
实例
is is是判断两个标识符是不是引用自一个对象 x is y, 如果 id(x) 等于 id(y) , is 返回结果 1
is not is not是判断两个标识符是不是引用自不同对象 x is not y, 如果 id(x) 不等于 id(y). is not返回结果 1
以下实例演示了python所有身份运算符的操作：
#!/usr/bin/python a = 20 b = 20 if ( a is b ): print "line 1 - a and b have same identity" else: print "line 1 - a and b do not have same identity" if ( id(a) == id(b) ): print "line 2 - a and b have same identity" else: print "line 2 - a and b do not have same identity" b = 30 if ( a is b ): print "line 3 - a and b have same identity" else: print "line 3 - a and b do not have same identity" if ( a is not b ): print "line 4 - a and b do not have same identity" else: print "line 4 - a and b have same identity"
以上实例输出结果：
line 1 - a and b have same identity
line 2 - a and b have same identity
line 3 - a and b do not have same identity
line 4 - a and b do not have same identity
python运算符优先级
以下表格列出了从最高到最低优先级的所有运算符：
运算符
描述
** 指数 (最高优先级)
~ + - 按位翻转, 一元加号和减号 (最后两个的方法名为 +@ 和 -@)
* / % // 乘，除，取模和取整除
+ - 加法减法
>> << 右移，左移运算符
& 位 'and'
^ | 位运算符
<= < > >= 比较运算符
<> == != 等于运算符
= %= /= //= -= += *= **= 赋值运算符
is is not 身份运算符
in not in 成员运算符
not or and 逻辑运算符
以下实例演示了python所有运算符优先级的操作：
#!/usr/bin/python a = 20 b = 10 c = 15 d = 5 e = 0 e = (a + b) * c / d #( 30 * 15 ) / 5 print "value of (a + b) * c / d is ", e e = ((a + b) * c) / d # (30 * 15 ) / 5 print "value of ((a + b) * c) / d is ", e e = (a + b) * (c / d); # (30) * (15/5) print "value of (a + b) * (c / d) is ", e e = a + (b * c) / d; # 20 + (150/5) print "value of a + (b * c) / d is ", e
以上实例输出结果：
value of (a + b) * c / d is 90
value of ((a + b) * c) / d is 90
value of (a + b) * (c / d) is 90
value of a + (b * c) / d is 50