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进攻Python第六战:运算符

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时间:2016-07-10 22:21来源:谷歌推广seo网络知识 作者:谷歌优化怎么做
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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 ", c

c = 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 ", c

a = 2b = 3c = a**b
print "Line 6 - Value of c is ", c

a = 10b = 5c = a//b print "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 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 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/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 ", c

c += 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 ", c

c **= aprint "Line 6 - Value of c is ", c

c //= 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 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 ,谷歌推广,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 ", c

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

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

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

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

c = 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 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/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 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/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 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/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 ",  e

e = ((a + b) * c) / d     # (30 * 15 ) / 5print "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 90Value of ((a + b) * c) / d is 90Value of (a + b) * (c / d) is 90Value of a + (b * c) / d is 50



来源:数据分析网( afenxi.com)

链接: afenxi.com/post/5126


(整理:英文推广TuiGuang123.com)
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