An article to help you understand the basics of Python and data types

1. Base system

1. What is base system?

The base system is also the carry counting system, which is an artificially defined counting method with carry (there are counting methods without carry, such as the original knot counting method, when counting votes Commonly used "positive" word counting, and similar tally mark counting). For any base system - the X base system, it means that the number operation at each position is carried out by one digit every time X is reached. The decimal system carries one after every tenth, the hexadecimal system carries forward every sixteenth, the binary system carries through every two, and so on, the x-based system carries forward every x. (From Baidu)

Popular explanation, the so-called base system is a method of counting. The base system means that when the base system is satisfied, one digit will be advanced to the high order. .

2. Base conversion

In Python, you can use the built-in function int() function to convert binary to decimal; the int() function can convert Convert a numeric string or decimal number in a specified base into an integer.

Syntax:

int(object,base)

Return value: Return the integer type data.

Convert binary number to decimal number

test = ['111011011111', '0b110']
for number in test:


    print(int(number, 2))

Run result:

将八进制数转化为十进制数。

test = ['-1537202', '125']


for number in test:
    print(int(number, 8))

运行 结果 ：

二、数值类型

1. 布尔型

布尔型其实是整型的子类型，布尔型数据只有两个取值：True和False，分别对应整型的1和0。

每一个Python对象都天生具有布尔值（True或False），进而可用于布尔测试（如用在if、while中）。

以下对象的布尔值都是False：

# 1. Python对象的布尔值
>>> bool(None)
False
>>> bool(False), bool(0), bool(0L), bool(0.0), bool(0.0+0.0j)
(False, False, False, False, False)
>>> bool(''), bool([]), bool(()), bool({})
(False, False, False, False)


# 2. 数值运算中，布尔值True和False分别对应整型的1和0
>>> int(True), int(2 < 1)
(1, 0)
>>> False + 100
100  #输出结果
>>> True + 100
101  #输出结果

>>> a = 0b10100 
>>> type(a)
int   #输出结果
>>> a
20  #输出结果
>>> bin(20), oct(20), hex(20)
('0b10100', '024', '0x14')  # 输出结果

>>> a = 999 ** 8  # 整型自动转换为长整型
>>> a
8920457944069944027201L
>>> type(a)
long

>>> type(1)
int   #输出结果
>>> type(1.0)
float  #输出结果
>>> 1 + 1.0
2.0  #输出结果
>>> a = 1e-2
>>> a  #输出结果
0.01
>>> type(a)
float   #输出结果
>>> pi = 3.1415926
>>> round(pi)
3.0  #输出结果
>>> round(pi, 4)
3.1416  #输出结果

>>> a = 1+2j
>>> a  
(1+2j)  #输出结果
>>> a.real # 实部
1.0     #输出结果
>>> type(a.real)
float   #输出结果
>>> a.imag # 虚部
2.0     #输出结果
>>> type(a.imag)
float   #输出结果