python的数据类型以及运算符号

整型

In [1]: a = 1     
                                                     
In [2]: print(a)                                                       
1

In [3]: type(a)                                                        
Out[3]: int

浮点型

In [4]: b = 1.2                                                        

In [5]: type(b)                                                        
Out[5]: float

字符串类型

In [6]: c = westos                                                              
---------------------------------------------------------------------------
NameError                                 Traceback (most recent call last)
<ipython-input-6-47a30bc3df16> in <module>
----> 1 c = westos

NameError: name 'westos' is not defined

In [7]: c = 'westos'                                                            

In [8]: type(c)                                                                 
Out[8]: str

类型转换

In [9]: float(a)      # a=1,b=1.2,c='westos'                                           
Out[9]: 1.0     

In [10]: int(b)       # 向下取整                                                
Out[10]: 1

In [11]: float(c)                                                               
---------------------------------------------------------------------------
ValueError                                Traceback (most recent call last)
<ipython-input-11-36b90e4449a0> in <module>
----> 1 float(c)

ValueError: could not convert string to float: 'westos'

In [12]: str(a)                                                                 
Out[12]: '1'

In [13]: str(b)                                                                 
Out[13]: '1.2'

In [14]: d = '123456'                                                           

In [15]: int(d)                                                                 
Out[15]: 123456

In [16]: float(d)                                                               
Out[16]: 123456.0

如何删除内存中的变量

In [17]: del a                                                                  

In [18]: a                                                                      
---------------------------------------------------------------------------
NameError                                 Traceback (most recent call last)
<ipython-input-18-3f786850e387> in <module>
----> 1 a

NameError: name 'a' is not defined

bool类型

bool:只有两个值(True False)
非0即真

In [19]: a = 1                                                                  

In [20]: bool(a)                                                                
Out[20]: True

In [21]: bool(0)                                                                
Out[21]: False

In [22]: bool(1)                                                                
Out[22]: True

In [23]: bool('')                # 中间无空格                                  
Out[23]: False

In [24]: bool(' ')               # 中间有空格                           
Out[24]: True

In [25]: bool(2412414)                                                          
Out[25]: True

运算符号

先乘除后加减
同级运算符是从左至右计算的
可以使用()调整计算的优先级

In [26]: 1+2
Out[26]: 3

In [27]: 3-1
Out[27]: 2

In [28]: 2*3
Out[28]: 6

In [29]: 6/3
Out[29]: 2.0

In [30]: 9/2      # " / "  表示浮点数除法，返回浮点结果
Out[30]: 4.5

In [31]: 9//2     # " // " 表示整数除法
Out[31]: 4		  # 向下取整

In [32]: 9%2      # 求余
Out[32]: 1

In [33]: 2**2     # 2的2次方
Out[33]: 4