运算

什么是操作符？
简单的回答可以使用表达式4 + 5等于9，在这里4和5被称为操作数，+被称为操符。 Python语言支持操作者有以下几种类型。
算术运算符
比较(即关系)运算符
赋值运算符
逻辑运算符
位运算符
会员操作符
标识操作符
让我们逐一看看所有的运算符。
Python算术运算符：
假设变量a持有10和变量b持有20，则： 
​操作符    描述符 例子
+   加法 - 对操作符的两侧增加值 a + b = 30
-   减法 - 减去从左侧操作数右侧操作数  a - b = -10
*   乘法 - 相乘的运算符两侧的值 a * b = 200
/   除 - 由右侧操作数除以左侧操作数   b / a = 2
%   模 - 由右侧操作数和余返回除以左侧操作数   b % a = 0
**  指数- 执行对操作指数（幂）的计算   a**b = 10 的幂 20
//  地板除 - 操作数的除法，其中结果是将小数点后的位数被除去的商。    9//2 =  4 而 9.0//2.0 = 4.0
#!/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

执行程序结果
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的比较操作符：
假设变量a持有10和变量b持有20，则：
运算符 描述  示例
==  检查，两个操作数的值是否相等，如果是则条件变为真。   (a == b) 不为 true.
!=  检查两个操作数的值是否相等，如果值不相等，则条件变为真。    (a != b) 为 true.
<>  检查两个操作数的值是否相等，如果值不相等，则条件变为真。    (a <> b) 为 true。这个类似于 != 运算符
>   检查左操作数的值是否大于右操作数的值，如果是，则条件成立。   (a > b) 不为 true.
<   检查左操作数的值是否小于右操作数的值，如果是，则条件成立。   (a < b) 为 true.
>=  检查左操作数的值是否大于或等于右操作数的值，如果是，则条件成立。    (a >= b) 不为 true.
<=  检查左操作数的值是否小于或等于右操作数的值，如果是，则条件成立。    (a <= b) 为 true.
#!/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"
当执行上面的程序它会产生以下结果：

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：
假设变量持有10和变量b持有20，则：
运算符 描述  示例
=   简单的赋值运算符，赋值从右侧操作数左侧操作数  c = a + b将指定的值 a + b 到  c
+=  加法AND赋值操作符，它增加了右操作数左操作数和结果赋给左操作数    c += a 相当于 c = c + a
-=  减AND赋值操作符，它减去右边的操作数从左边操作数，并将结果赋给左操作数    c -= a 相当于 c = c - a
*=  乘法AND赋值操作符，它乘以右边的操作数与左操作数，并将结果赋给左操作数    c *= a 相当于 c = c * a
/=  除法AND赋值操作符，它把左操作数与正确的操作数，并将结果赋给左操作数 c /= a 相当于= c / a
%=  模量AND赋值操作符，它需要使用两个操作数的模量和分配结果左操作数   c %= a is equivalent to c = c % a
**= 指数AND赋值运算符，执行指数（功率）计算操作符和赋值给左操作数    c **= a 相当于 c = c ** a
//= 地板除，并分配一个值，执行地板除对操作和赋值给左操作数 c //= a 相当于 c = c // a
#!/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
当执行上面的程序，它会产生以下结果：

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：
位运算符作用于位和位操作执行位。假设，如果a =60;且b =13;现在以二进制格式它们将如下：
a = 0011 1100
b = 0000 1101
-----------------
a&b = 0000 1100
a|b = 0011 1101
a^b = 0011 0001
~a  = 1100 0011
Python语言支持下位运算符
操作符 描述  示例
&   二进制和复制操作了一下，结果，如果它存在于两个操作数。 (a & b) = 12 即 0000 1100
|   二进制或复制操作了一个比特，如果它存在一个操作数中。  (a | b) = 61 即 0011 1101
^   二进制异或运算符的副本，如果它被设置在一个操作数而不是两个比特。    (a ^ b) =  49 即  0011 0001
~   二进制的补运算符是一元的，并有“翻转”位的效果。    (~a ) =  -61 即 1100 0011以2的补码形式由于带符号二进制数。
<<  二进位向左移位运算符。左操作数的值左移由右操作数指定的位数。  a << 2 = 240 即 1111 0000
>>  二进位向右移位运算符。左操作数的值是由右操作数指定的位数向右移动。   a >> 2 = 15 即 0000 1111
#!/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
当执行上面的程序它会产生以下结果：

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语言支持以下逻辑运算符。假设变量a持有10和变量b持有20则：
运算符 描述  示例
and 所谓逻辑与运算符。如果两个操作数都是真的，那么则条件成立。   (a and b) 为 true.
or  所谓逻辑OR运算符。如果有两个操作数都是非零然后再条件变为真。 (a or b) 为 true.
not 所谓逻辑非运算符。用于反转操作数的逻辑状态。如果一个条件为真，则逻辑非运算符将返回false。 not(a and b) 为 false.
#!/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"else:
   print "Line 5 - a and b are true"
当执行上面的程序它会产生以下结果：

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
Python成员运算符：
除了前面讨论的运算符，Python成员运算符，在一个序列中成员资格的测试，如字符串，列表或元组。有两个成员运算符解释如下：
操作符 描述  示例
in  计算结果为true，如果它在指定找到变量的顺序，否则false。    x在y中，在这里产生一个1，如果x是序列y的成员。
not in  计算结果为true，如果它不找到在指定的变量顺序，否则为false。  x不在y中，这里产生结果不为1，如果x不是序列y的成员。
#!/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"
当执行上面的程序它会产生以下结果：

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标识运算符：
标识符比较两个对象的内存位置。两个运算符标识解释如下：
运算符 描述  例子
is  计算结果为true，如果操作符两侧的变量指向相同的对象，否则为false。   x是y，这里结果是1，如果id（x）的值为id（y）。
is not  计算结果为false，如果两侧的变量操作符指向相同的对象，否则为true。   x不为y，这里结果不是1，当id（x）不等于id（y）。
#!/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"
当执行上面的程序它会产生以下结果：

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
下表列出了所有运算符从最高优先级到最低。

运算符 描述
**  幂（提高到指数）
~ + -   补码，一元加号和减号（方法名的最后两个+@和 - @）
* / % //    乘，除，取模和地板除
+ - 加法和减法
>> <<   左，右按位转移
&   位'AND'
^ | 按位异'或`'和定期`或'
<= < > >=   比较运算符
<> == !=    等式运算符
= %= /= //= -= += *= **=    赋值运算符
is is not   标识运算符
in not in   成员运算符
not or and  逻辑运算符
#!/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
当执行上面的程序，它会产生以下结果：

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