Python-运算符

>>> a = 21
>>> b = 10
>>> c = a + b      #变量相加
>>> print (c)
31
>>> c = a - b        #变量相见
>>> print (c)
11
>>> c = a * b        #变量相乘
>>> print (c)
210
>>> c = a / b         #变量相除
>>> print (c)
2.1
>>> c = a % b        #取模-返回两个变量的余数
>>> print (c)
1
>>> c = a**b         #幂，也就是a的b次方
>>> print (c)
16679880978201
>>> c = a // b         #两数相乘取整数
>>> print (c)
2
>>>

>>>a = 21
>>>b = 10
>>> a == b
False
>>> a != b
True
>>> a > b
True
>>> a < b
False
>>> a >= b
True
>>> a <= b
False
>>>

a = 21
b = 10
if a == b:
    print("1-a等于变量b")
else:
    print("1-a不等于变量b")
if ( a != b ):
   print ("2-a 不等于 b")
else:
   print ("2-a 等于 b")

if ( a < b ):
   print ("3-a 小于 b")
else:
   print ("3-a 大于等于 b")

if ( a > b ):
   print ("4-a大于 b")
else:
   print ("4-a小于等于 b")

if ( a <= b ):
   print ("5-a 小于等于 b")
else:
   print ("5-a 大于  b")

if ( b >= a ):
   print ("6-b 大于等于 a")
else:
   print ("6-b 小于 a")
输出如下
1-a不等于变量b
2-a 不等于 b
3-a 大于等于 b
4-a大于 b
5-a 大于  b
6-b 小于 a

>>> print (a)
21
>>> print (b)
10
>>> c = a + b
>>> print (c)
31
>>> a += b     #等于直接把两个变量相加得的值赋给了a
>>> print (a)
31
>>>a -= b       
>>> print (a)
21
>>>

>>> print (a)
21
>>> print (b)
10
>>> a and b  #如果a为真则返回b的值
10
>>> a or b     #如果a是真则返回a，否则返回b
21
>>> not a      #如果a为真则返回假，如果a为假则返回真
False

>>> a = "huige"        
>>> b = 3
>>> list = ["Alex","huige","Lisa",8]       #定义一个列表
>>> list
[‘Alex‘, ‘huige‘, ‘Lisa‘, 8]  
>>> a in list                                          #a 如果在列表中返回True
True
>>> a = "hui"
>>> a in list                                          #a 不在列表中返回Flase
False
>>> a not in list                                   #not in 整好取反 a不在列表中返True
True
>>> b in list                                         
False
>>> b not in list                                  #b 不在列表中返回True
True
>>>

>>> a = 2                    #定义两个变量
>>> b = "huige"           
>>> a is b                   #a的id和b的id不同 所以使用身份运算符is判断返回False
False
>>> id(a)                    #查看a的id   
1870262096
>>> id(b)                     #查看b的id
380323631824
>>> a is not b              # is not 整好取反 不相同返回True
True
>>> b = 3
>>> a is b
False
>>> a is not b         
True
>>> b = 2                     #给变量b赋值为2
>>> a is b
True
>>> a is not b                # is not 整好取反 相同返回False
False
>>> id(a)                       #id相同
1870262096
>>> id(b)
1870262096
>>>