【2015.08.29】6.Python运算符

1250阅读　0评论2015-08-29　Joker_ora
分类：Python/Ruby

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:

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：

点击(此处)折叠或打开

  1. #!/usr/bin/python

  3. a = 21
  4. b = 10
  5. c = 0

  7. c = a + b
  8. print "Line 1 - Value of c is ", c

  10. c = a - b
  11. print "Line 2 - Value of c is ", c

  13. c = a * b
  14. print "Line 3 - Value of c is ", c

  16. c = a / b
  17. print "Line 4 - Value of c is ", c

  19. c = a % b
  20. print "Line 5 - Value of c is ", c

  22. a = 2
  23. b = 3
  24. c = a**b
  25. print "Line 6 - Value of c is ", c

  27. a = 10
  28. b = 5
  29. c = a//b
  30. print "Line 7 - Value of c is ", c
以上实例输出结果：

点击(此处)折叠或打开

  1. Line 1 - Value of c is 31
  2. Line 2 - Value of c is 11
  3. Line 3 - Value of c is 210
  4. Line 4 - Value of c is 2
  5. Line 5 - Value of c is 1
  6. Line 6 - Value of c is 8
  7. 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：

点击(此处)折叠或打开

  1. #!/usr/bin/python

  3. a = 21
  4. b = 10
  5. c = 0

  7. if ( a == b ):
  8.    print "Line 1 - a is equal to b"
  9. else:
  10.    print "Line 1 - a is not equal to b"

  12. if ( a != b ):
  13.    print "Line 2 - a is not equal to b"
  14. else:
  15.    print "Line 2 - a is equal to b"

  17. if ( a <> b ):
  18.    print "Line 3 - a is not equal to b"
  19. else:
  20.    print "Line 3 - a is equal to b"

  22. if ( a < b ):
  23.    print "Line 4 - a is less than b"
  24. else:
  25.    print "Line 4 - a is not less than b"

  27. if ( a > b ):
  28.    print "Line 5 - a is greater than b"
  29. else:
  30.    print "Line 5 - a is not greater than b"

  32. a = 5;
  33. b = 20;
  34. if ( a <= b ):
  35.    print "Line 6 - a is either less than or equal to b"
  36. else:
  37.    print "Line 6 - a is neither less than nor equal to b"

  39. if ( b >= a ):
  40.    print "Line 7 - b is either greater than or equal to b"
  41. else:
  42.    print "Line 7 - b is neither greater than nor equal to b"

  44. 以上实例输出结果：

  46. Line 1 - a is not equal to b
  47. Line 2 - a is not equal to b
  48. Line 3 - a is not equal to b
  49. Line 4 - a is not less than b
  50. Line 5 - a is greater than b
  51. Line 6 - a is either less than or equal to b
  52. 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：

点击(此处)折叠或打开

  1. #!/usr/bin/python

  3. a = 21
  4. b = 10
  5. c = 0

  7. c = a + b
  8. print "Line 1 - Value of c is ", c

  10. c += a
  11. print "Line 2 - Value of c is ", c

  13. c *= a
  14. print "Line 3 - Value of c is ", c

  16. c /= a
  17. print "Line 4 - Value of c is ", c

  19. c = 2
  20. c %= a
  21. print "Line 5 - Value of c is ", c

  23. c **= a
  24. print "Line 6 - Value of c is ", c

  26. c //= a
  27. print "Line 7 - Value of c is ", c

以上实例输出结果：

点击(此处)折叠或打开

  1. Line 1 - Value of c is 31
  2. Line 2 - Value of c is 52
  3. Line 3 - Value of c is 1092
  4. Line 4 - Value of c is 52
  5. Line 5 - Value of c is 2
  6. Line 6 - Value of c is 2097152
  7. 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

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：

点击(此处)折叠或打开

  1. #!/usr/bin/python

  3. a = 60 # 60 = 0011 1100
  4. b = 13 # 13 = 0000 1101
  5. c = 0

  7. c = a & b; # 12 = 0000 1100
  8. print "Line 1 - Value of c is ", c

  10. c = a | b; # 61 = 0011 1101
  11. print "Line 2 - Value of c is ", c

  13. c = a ^ b; # 49 = 0011 0001
  14. print "Line 3 - Value of c is ", c

  16. c = ~a; # -61 = 1100 0011
  17. print "Line 4 - Value of c is ", c

  19. c = a << 2; # 240 = 1111 0000
  20. print "Line 5 - Value of c is ", c

  22. c = a >> 2; # 15 = 0000 1111
  23. print "Line 6 - Value of c is ", c

以上实例输出结果：

点击(此处)折叠或打开

  1. Line 1 - Value of c is 12
  2. Line 2 - Value of c is 61
  3. Line 3 - Value of c is 49
  4. Line 4 - Value of c is -61
  5. Line 5 - Value of c is 240
  6. 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：

点击(此处)折叠或打开

  1. #!/usr/bin/python

  3. a = 10
  4. b = 20
  5. c = 0

  7. if ( a and b ):
  8.    print "Line 1 - a and b are true"
  9. else:
  10.    print "Line 1 - Either a is not true or b is not true"

  12. if ( a or b ):
  13.    print "Line 2 - Either a is true or b is true or both are true"
  14. else:
  15.    print "Line 2 - Neither a is true nor b is true"


  18. a = 0
  19. if ( a and b ):
  20.    print "Line 3 - a and b are true"
  21. else:
  22.    print "Line 3 - Either a is not true or b is not true"

  24. if ( a or b ):
  25.    print "Line 4 - Either a is true or b is true or both are true"
  26. else:
  27.    print "Line 4 - Neither a is true nor b is true"

  29. if not( a and b ):
  30.    print "Line 5 - Either a is not true or b is not true or both are not true"
  31. else:
  32.    print "Line 5 - a and b are true"
  33. 以上实例输出结果：

  35. Line 1 - a and b are true
  36. Line 2 - Either a is true or b is true or both are true
  37. Line 3 - Either a is not true or b is not true
  38. Line 4 - Either a is true or b is true or both are true
  39. Line 5 - Either a is not true or b is not true or both are not true

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：


点击(此处)折叠或打开

  1. #!/usr/bin/python

  3. a = 20
  4. b = 20

  6. if ( a is b ):
  7.    print "Line 1 - a and b have same identity"
  8. else:
  9.    print "Line 1 - a and b do not have same identity"

  11. if ( id(a) == id(b) ):
  12.    print "Line 2 - a and b have same identity"
  13. else:
  14.    print "Line 2 - a and b do not have same identity"

  16. b = 30
  17. if ( a is b ):
  18.    print "Line 3 - a and b have same identity"
  19. else:
  20.    print "Line 3 - a and b do not have same identity"

  22. if ( a is not b ):
  23.    print "Line 4 - a and b do not have same identity"
  24. else:
  25.    print "Line 4 - a and b have same identity"
  26. 以上实例输出结果：

  28. Line 1 - a and b have same identity
  29. Line 2 - a and b have same identity
  30. Line 3 - a and b do not have same identity
  31. 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：


点击(此处)折叠或打开

  1. #!/usr/bin/python

  3. a = 20
  4. b = 10
  5. c = 15
  6. d = 5
  7. e = 0

  9. e = (a + b) * c / d #( 30 * 15 ) / 5
  10. print "Value of (a + b) * c / d is ", e

  12. e = ((a + b) * c) / d # (30 * 15 ) / 5
  13. print "Value of ((a + b) * c) / d is ", e

  15. e = (a + b) * (c / d); # (30) * (15/5)
  16. print "Value of (a + b) * (c / d) is ", e

  18. e = a + (b * c) / d; # 20 + (150/5)
  19. print "Value of a + (b * c) / d is ", e
  20. 以上实例输出结果：

  22. Value of (a + b) * c / d is 90
  23. Value of ((a + b) * c) / d is 90
  24. Value of (a + b) * (c / d) is 90
  25. Value of a + (b * c) / d is 50











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