数据类型--运算符和表达式

python语言支持下列类型的运算符

1、算术运算符
2、比较（关系）运算符
3、赋值运算符
4、位运算符
5、逻辑运算符
6、成员运算符
7、身份运算符
8、运算符优先级

 

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

 

 1 #!/usr/bin/python
 2 a = 21
 3 b = 10
 4 c = 0
 5 
 6 c=a + b
 7 print("Line 1 - value of c is ",c)
 8 
 9 c=a - b
10 print("Line 2 - value of c is ",c)
11 
12 c=a * b 
13 print("Line 3 - values of c is ",c)
14 
15 
16 c=a / b
17 print("Line 4 - value of c is ",c)
18 
19 
20 c= a % b
21 print("Line 5 - value of c is ",c)
22 
23 
24 a = 2
25 b = 3
26 c = a**b
27 print("Line 6 - value if c is ",c)
28 
29 a = 10
30 b = 5
31 c = a//b
32 print("Line 7 - value of c is ",c)
33 
34 
35 
36 输出结果：
37 Line 1 - value of c is  31
38 Line 2 - value of c is  11
39 Line 3 - values of c is  210
40 Line 4 - value of c is  2.1
41 Line 5 - value of c is  1
42 Line 6 - value if c is  8
43 Line 7 - value of c is  2
算术运算符练习

 

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（3.0已经取消） (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。 
 1 a = 21
 2 b = 10
 3 c = 0
 4 
 5 if ( a == b ):
 6     print("Line 1 - a is equal to b")
 7 else:
 8     print("Line 1 - a is not equal to b")
 9 
10 if ( a != b ):
11     print("Line 2 - a is not equal to b")
12 else:
13     print("Line 2 - a is equal to b")
14 
15 # if ( a <> b ):
16 #     print("Line 3 - a is not equal to b")
17 # else:
18 #     print("Line 3 - a is equal to b")
19 
20 
21 if ( a < b ):
22     print("Line 4 - a is less than b")
23 else:
24     print("Line 4 - a is not less than b")
25 
26 
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")
31 
32 
33 a = 5
34 b = 20
35 if ( a <= b ):
36     print("Line 6 - is either less than or equal to b")
37 else:
38     print("Line 6 - is neither less than nor equal to b")
39 
40 
41 if ( b >= a ):
42     print("Line 7 - is either greater than or equal to b")
43 else:
44     print("Line 7 - is neither greater than nor equal to b")
45 
46 
47 
48 输出显示：
49 Line 1 - a is not equal to b
50 Line 2 - a is not equal to b
51 Line 4 - a is not less than b
52 Line 5 - a is greater than b
53 Line 6 - is either less than or equal to b
54 Line 7 - is either greater than or equal to b
55 
56 
57 
58 注意：
59 在3.0以上的python代码中，去掉了不等于"<>" 这个比较运算符。
60 
61 如下：
62 
63     if ( a <> b ):
64             ^
65 SyntaxError: invalid syntax
比较运算符练习

 

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 
 1 #!/usr/bin/python
 2 a = 21
 3 b = 10
 4 c = 0
 5 
 6 c = a + b
 7 print("Line 1 - value of c is", c)
 8 
 9 c += a
10 print("Line 2 - value of c is", c)
11 
12 c *= a
13 print("Line 3 - value of c is", c)
14 
15 c /= a
16 print("Line 4 - value of c is", c)
17 
18 c = 2
19 c %= a
20 print("Line 5 - value of c is", c)
21 
22 c **= a
23 print("Line 6 - value of c is", c)
24 
25 c //= a
26 print("Line 7 - value of c is", c)
27 
28 
29 
30 输出结果：
31 Line 1 - value of c is 31
32 Line 2 - value of c is 52
33 Line 3 - value of c is 1092
34 Line 4 - value of c is 52.0
35 Line 5 - value of c is 2
36 Line 6 - value of c is 2097152
37 Line 7 - value of c is 99864
View Code

 

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 
 1 #!/usr/bin/python
 2 a = 60    #60 = 0011 1100
 3 b = 13    #60 = 0000 1101
 4 c = 0
 5 
 6 c = a & b;   # 12 = 0000 1100
 7 print("Line 1 - Value of c is", c)
 8 
 9 c = a | b;   # 61 = 0011 1101
10 print("Line 2 - value of c is", c)
11 
12 c = a ^ b;   # 49 = 0011 0001
13 print("Line 3 - value of c is", c)
14 
15 c = ~a;      # -61 = 1100 0011
16 print("Line 4 - value of c is", c)
17 
18 c = a << 2;  # 240 = 1111 0000
19 print("Line 5 - value of c is", c)
20 
21 c = a >> 2;  # 15 = 0000 1111
22 print=("Line 6 - value of c is", c)
23 
24 输出结果：
25 Line 1 - Value of c is 12
26 Line 2 - value of c is 61
27 Line 3 - value of c is 49
28 Line 4 - value of c is -61
29 Line 5 - value of c is 240
位运算符练习

 

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。 

 

 1 #!/usr/bin/python
 2 a = 10
 3 b = 20
 4 c = 0
 5 
 6 if ( a and b ):
 7     print("Line 1 - a and b are true")
 8 else:
 9     print("Line 1 - Either a is not true or b is not true")
10 
11 if( a or b ):
12     print("Line 2 - Either a is true or b is true or both are true")
13 else:
14     print("Line 2 - Neither a is true nor b is true")
15 
16 
17 a = 0
18 if( a and b ):
19     print("Line 3 -a and b are true")
20 else:
21     print("Line 3 - Either a is not true or b is not true")
22 
23 if ( a or b ):
24     print("Line 4 - Either a is true or b is true or both are true")
25 else:
26     print("Line 4 - Neither a is true nor b is true")
27 
28 if ( a and b ):
29     print("Line 5 - Either a is not true or b is not true or both are not true")
30 else:
31     print("Line 5 - a and b are true")
32 
33 
34 
35 
36 输出结果：
37 Line 1 - a and b are true
38 Line 2 - Either a is true or b is true or both are true
39 Line 3 - Either a is not true or b is not true
40 Line 4 - Either a is true or b is true or both are true
41 Line 5 - a and b are true
逻辑运算符练习

 

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。

 

 1 #!/usr/bin/python
 2 
 3 a = 10
 4 
 5 b = 20
 6 
 7 list = [1,2,3,4,5];
 8 
 9 
10 if ( a in list ):
11 
12     print("Line 1 - a is available in the given list")
13 
14 else:
15 
16     print("Line 1 - a is not available in the given list")
17 
18 
19 
20 if ( b not in list ):
21 
22     print("Line 2 - b is not available in the given list")
23 
24 else:
25 
26     print("Line 2 - b is available in the given list")
27 
28 
29 
30 a = 2
31 
32 if ( a in list ):
33 
34     print("Line 3 - a is available in the given list")
35 
36 else:
37 
38     print("Line 3 - a is not available in the given list")
39 
40 
41 输出结果：
42 Line 1 - a is not available in the given list
43 Line 2 - b is not available in the given list
44 Line 3 - a is available in the given list
成员运算符练习

 

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 

 

 1 #!/usr/bin/python
 2 a = 20
 3 b = 20
 4 
 5 if ( a is b ):
 6     print("Line 1 - a and b have same identity")
 7 else:
 8     print("Line 1 - a and b do not have same identify")
 9 
10 if ( id(a) == id(b) ):
11     print("Line 2 - a and b have same identity")
12 else:
13     print("Line 2 - a and b do not have same identity")
14 
15 b = 30
16 if ( a is b ):
17     print("Line 3 - a and b have same identity")
18 else:
19     print("Line 3 - a and b do not have same identity")
20 
21 if ( a is not b ):
22     print("Line 4 - a and b do not have same identity")
23 else:
24     print("Line 4 - a and b have same identity")
25 
26 
27 显示结果：
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
身份运算符练习

 

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 
 1 #!/usr/bin/python
 2 
 3 a = 20
 4 b = 10
 5 c = 15
 6 d = 5
 7 e = 0
 8 
 9 e = ( a + b )* c / d    #(20+10)*15/5
10 print("value of (a+b)*c/d is ", e)
11 
12 e = (( a + b ) * c) / d  #((20+10)*15)/5
13 print("value of (a+b)*c/d is ", e)
14 
15 e = ( a + b ) * ( c / d ) #(20+10)*(15/5)
16 print("value of (a+b)*(c/d) is ", e)
17 
18 e= a + ( b * c ) / d   #20 + ( 10 * 15 ) / 5
19 print("value of a+(b*c)/d os ", e)
20 
21 
22 输出结果：
23 value of (a+b)*c/d is  90.0
24 value of (a+b)*c/d is  90.0
25 value of (a+b)*(c/d) is  90.0
26 value of a+(b*c)/d os  50.0
运算符优先级练习

 

posted @ 2017-12-13 11:02  风之岚翔  阅读(326)  评论(0)  编辑  收藏  举报