Python 运算符

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 为10的20次方， 输出结果 100000000000000000000// 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/pythona = 21b = 10c = 0c = a + bprint "Line 1 - Value of c is ", cc = a - bprint "Line 2 - Value of c is ", c c = a * bprint "Line 3 - Value of c is ", c c = a / bprint "Line 4 - Value of c is ", c c = a % bprint "Line 5 - Value of c is ", ca = 2b = 3c = a**b print "Line 6 - Value of c is ", ca = 10b = 5c = a//b print "Line 7 - Value of c is ", c

尝试一下 »

以上实例输出结果：

Line 1 - Value of c is 31Line 2 - Value of c is 11Line 3 - Value of c is 210Line 4 - Value of c is 2Line 5 - Value of c is 1Line 6 - Value of c is 8Line 7 - Value of c is 2Python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/pythona = 21b = 10c = 0if ( 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 bLine 2 - a is not equal to bLine 3 - a is not equal to bLine 4 - a is not less than bLine 5 - a is greater than bLine 6 - a is either less than or equal to bLine 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/pythona = 21b = 10c = 0c = a + bprint "Line 1 - Value of c is ", cc += aprint "Line 2 - Value of c is ", c c *= aprint "Line 3 - Value of c is ", c c /= a print "Line 4 - Value of c is ", c c = 2c %= aprint "Line 5 - Value of c is ", cc **= aprint "Line 6 - Value of c is ", cc //= aprint "Line 7 - Value of c is ", c

以上实例输出结果：

Line 1 - Value of c is 31Line 2 - Value of c is 52Line 3 - Value of c is 1092Line 4 - Value of c is 52Line 5 - Value of c is 2Line 6 - Value of c is 2097152Line 7 - Value of c is 99864Python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/pythona = 60 # 60 = 0011 1100 b = 13 # 13 = 0000 1101 c = 0c = a & b;# 12 = 0000 1100print "Line 1 - Value of c is ", cc = a | b;# 61 = 0011 1101 print "Line 2 - Value of c is ", cc = a ^ b;# 49 = 0011 0001print "Line 3 - Value of c is ", cc = ~a; # -61 = 1100 0011print "Line 4 - Value of c is ", cc = a << 2; # 240 = 1111 0000print "Line 5 - Value of c is ", cc = a >> 2; # 15 = 0000 1111print "Line 6 - Value of c is ", c

以上实例输出结果：

Line 1 - Value of c is 12Line 2 - Value of c is 61Line 3 - Value of c is 49Line 4 - Value of c is -61Line 5 - Value of c is 240Line 6 - Value of c is 15Python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/pythona = 10b = 20c = 0if ( 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 = 0if ( 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 - Either a is not true or b is not true or both are not true"else: print "Line 5 - a and b are true"

以上实例输出结果：

Line 1 - a and b are trueLine 2 - Either a is true or b is true or both are trueLine 3 - Either a is not true or b is not trueLine 4 - Either a is true or b is true or both are trueLine 5 - Either a is not true or b is not true or both are not truePython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/pythona = 10b = 20list = [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 = 2if ( 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 listLine 2 - b is not available in the given listLine 3 - a is available in the given listPython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 1is 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/pythona = 20b = 20if ( 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 = 30if ( 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 identityLine 2 - a and b have same identityLine 3 - a and b do not have same identityLine 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/pythona = 20b = 10c = 15d = 5e = 0e = (a + b) * c / d #( 30 * 15 ) / 5print "Value of (a + b) * c / d is ", ee = ((a + b) * c) / d # (30 * 15 ) / 5print "Value of ((a + b) * c) / d is ", ee = (a + b) * (c / d); # (30) * (15/5)print "Value of (a + b) * (c / d) is ", ee = 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 90Value of ((a + b) * c) / d is 90Value of (a + b) * (c / d) is 90Value of a + (b * c) / d is 50