[TOC]
>本章節主要說明Python的運算符。舉個簡單的例子 4 +5 = 9 。 例子中，4和5被稱為操作數，"+"號為運算符。
Python語言支持以下類型的運算符:
- 算術運算符
- 比較（關系）運算符
- 賦值運算符
- 邏輯運算符
- 位運算符
- 成員運算符
- 身份運算符
- 運算符優先級
接下來讓我們一個個來學習Python的運算符。
# Python算術運算符
以下假設變量a為10，變量b為20：
| 運算符 | 描述 | 實例 |
| --- | --- | --- | --- |
| + | 加 - 兩個對象相加 | a + b 輸出結果 30
| - | 減 - 得到負數或是一個數減去另一個數 | a - b 輸出結果 -10
| * | 乘 - 兩個數相乘或是返回一個被重復若干次的字符串 | a * b 輸出結果 200
| / | 除 - x除以y b / a 輸出結果 2
| % | 取模 - 返回除法的余數 | b % a 輸出結果 0
| ** | 冪 - 返回x的y次冪 | a**b 為10的20次方， 輸出結果 100000000000000000000
// 取整除 - 返回商的整數部分 9//2 輸出結果 4 , 9.0//2.0 輸出結果 4.0
以下實例演示了Python所有算術運算符的操作：
```
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
嘗試一下 ?
以上實例輸出結果：
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比較運算符
以下假設變量a為10，變量b為20：
| 運算符 | 描述 | 實例 |
| --- | --- | --- | --- |
| == | 等于 | 比較對象是否相等 (a == b) 返回 False。|
| != | 不等于 | 比較兩個對象是否不相等 (a != b) 返回 true.|
| > | 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。所有比較運算符返回1表示真，返回0表示假。這分別與特殊的變量True和False等價。注意，這些變量名的大寫。 (a
| >= | 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
```
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"
以上實例輸出結果：
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賦值運算符
以下假設變量a為10，變量b為20：
| 運算符 | 描述 | 實例 |
| --- | --- | --- | --- |
= 簡單的賦值運算符 c = a + b 將 a + b 的運算結果賦值為 c
+= 加法賦值運算符 c += a 等效于 c = c + a
-= 減法賦值運算符 c -= a 等效于 c = c - a
*= 乘法賦值運算符 c *= a 等效于 c = c * a
/= 除法賦值運算符 c /= a 等效于 c = c / a
%= 取模賦值運算符 c %= a 等效于 c = c % a
**= 冪賦值運算符 c **= a 等效于 c = c ** a
//= 取整除賦值運算符 c //= a 等效于 c = c // a
以下實例演示了Python所有賦值運算符的操作：
```
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
以上實例輸出結果：
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位運算符
按位運算符是把數字看作二進制來進行計算的。Python中的按位運算法則如下：
| 運算符 | 描述 | 實例 |
| --- | --- | --- | --- |
& 按位與運算符 (a & b) 輸出結果 12 ，二進制解釋： 0000 1100
按位或運算符 (a b) 輸出結果 61 ，二進制解釋： 0011 1101
^ 按位異或運算符 (a ^ b) 輸出結果 49 ，二進制解釋： 0011 0001
~ 按位取反運算符 (~a ) 輸出結果 -61 ，二進制解釋： 1100 0011， 在一個有符號二進制數的補碼形式。
左移動運算符 a
>> 右移動運算符 a >> 2 輸出結果 15 ，二進制解釋： 0000 1111
以下實例演示了Python所有位運算符的操作：
```
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
以上實例輸出結果：
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邏輯運算符
Python語言支持邏輯運算符，以下假設變量a為10，變量b為20：
| 運算符 | 描述 | 實例 |
| --- | --- | --- | --- |
| and | 布爾"與" | 如果x為False，x and y返回False，否則它返回y的計算值。 (a and b) 返回 true。|
| or 布爾"或" | 如果x是True，它返回True，否則它返回y的計算值。| (a or b) 返回 true。|
| not 布爾"非" | 如果x為True，返回False。如果x為False，它返回True。| not(a and b) 返回 false。|
```
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"
以上實例輸出結果：
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成員運算符
除了以上的一些運算符之外，Python還支持成員運算符，測試實例中包含了一系列的成員，包括字符串，列表或元組。
| 運算符 | 描述 | 實例 |
| --- | --- | --- | --- |
| in | 如果在指定的序列中找到值返回True，否則返回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沒有找到值返回True，否則返回False。| x 不在 y序列中 , 如果x不在y序列中返回True。|
```
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"
以上實例輸出結果：
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身份運算符
身份運算符用于比較兩個對象的存儲單元
| 運算符 | 描述 | 實例 |
| --- | --- | --- | --- |
| is | is是判斷兩個標識符是不是引用自一個對象 | x is y, 如果 id(x) 等于 id(y) , is 返回結果 1 |
| is not | is not是判斷兩個標識符是不是引用自不同對象 x is not y, 如果 id(x) 不等于 id(y). is not 返回結果 1 |
```
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"
以上實例輸出結果：
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運算符優先級
> 使用 () 解決
