File operations in Python in a small note

Simple to open the head, recently in the study of Python, want to make a simple note, so wrote this article

First of all, say that there are many modules in Python, divided into the system and the external, here I will briefly introduce about the binary file

Conversion and storage, then the package used today is "struct", first introduce the "struct" inside two more useful things, one is

"Struct.pack (" I ", a)", this is the conversion of a decimal number into a binary, where the parameters I explain in the back. Another more useful

Is "Struct.unpack (" I ", bytesint)", needless to say, this is to turn the binary into decimal, then I will use the Python code

Introduce the use of these two functions and some other small knowledge

1.struct.pack

Import struct #导入struct模块

a,b,c=12,10,5

Bytesint=struct.pack ("III", A,b,c) #其中i是int类型的意思, several integers, corresponding to several I

Print (Bytesint) #打印出后 (an int, accounting for four bytes) = "

B ' \x0c\x00\x00\x00\n\x00\x00\x00\x05\x00\x00\x00 '

File=open ("BytesFile.txt", "WB") #输入一个二进制文本, BytesFile.txt is the name of the text,

WB is binary text write, RB is binary text read in

File.write (bytesint) #把bytesInt write bytesFile.txt inside

File.close () #关闭文件

#好了, the above is the simple application of "Struct.pack". Other types I think everyone will extrapolate.

2.struct.unpack

Import struct

File=open ("BytesFile.txt", "RB") #我在这里打开一个二进制的文本,

I'm going to put the bytesint in the BytesFile.txt.

Datas=file.read (4) #我在这里读file because int accounts for four bytes, so read (4),

Data=struct.unpack ("I", datas) [0] #里面参数与上面一样, but much explained, where the bytes actually

can also be viewed as a list, so I take the first byte [0]

Print (data) #打印出后 = "12

File.close () #每一次打开文件, remember to turn it off OH

3.bytes,encode, decode

S= "World"

L=s.encode ("Utf-8") utf-8 encoding s for #以utf-8 format

Print (l) # after printing = "B ' \xe4\xb8\x96\xe7\x95\x8c '

Print (L.decode ("Utf-8")) #打印出后 decoding = "World

Print (bytes (s, "Utf-8")) #打印出后 turn str into byte format, with encode= effect

B ' \xe4\xb8\x96\xe7\x95\x8c '

The first attribute value of 4.pack (transferred from official: https://docs.python.org/3/library/struct.html)

Standard

Format	C Type	Python Type	size	Notes
x	Pad byte	No value
c	char	bytes of length 1	1
b	signed char	Integer	1	(1), (3)
B	unsigned char	Integer	1	(3)
?	_Bool	bool	1	(1)
h	short	Integer	2	(3)
H	unsigned short	Integer	2	(3)
i	int	Integer	4	(3)
I	unsigned int	Integer	4	(3)
l	long	Integer	4	(3)
L	unsigned long	Integer	4	(3)
q	long long	Integer	8	(2), (3)
Q	unsigned long long	Integer	8	(2), (3)
n	ssize_t	Integer		(4)
N	size_t	Integer		(4)
e	(7)	Float	2	(5)
f	float	Float	4	(5)
d	double	Float	8	(5)
s	char[]	bytes
p	char[]	bytes
P	void *	Integer		(6)

　　

OK, it's here today, there are updates in the back oh (if there are errors, please correct, thank you OH):)

　　　　　　　　　　　　　　　　

　　　　

File operations in Python in a small note