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Python 运算符

category: 编程语言

什么是运算符？

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yb / 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/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  -  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  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  -  Either  a  is  not  true  or  b  is    not  true  or  both  are  not  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
isis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 notis 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