Python diary----2017.7.24

Character encoding

1 What encoding is stored and what code will be taken out
PS: Memory is fixed using Unicode encoding,
We can control the encoding is to the hard disk storage or based on the network transmission selection code

2 data is first generated in memory and is in Unicode format, to be transferred to bytes format
#unicode----->encode (utf-8)------>bytes
If you get bytes, you can store it in a file or network-based transmission.
#bytes------>decode (GBK)------->unicode

3 Python3 string is recognized as Unicode
The string encode in Python3 gets bytes

4 See
The string in Python2 is bytes
Python2 in front of the string is Unicode

File processing

1. Read-only mode ' R ': can only read the file, the file does not exist will be an error.

Read (): Read file

Open (): Opening file

Close (): Close file {Be sure to close}

ReadLine (): Execution of a row

ReadLines (): reads all the lines, and saves them in the form of a list

Readable: () detects whether the file is readable, returns TRUE or False

2. write-only mode; ' W ', file does not exist then create, empty existing

Writeable (): detects if the file is writable, returns TRUE or False

The Write (str) argument is a string that is the content you want to write to the file.

The Writelines (sequence) parameter is a sequence, such as a list, that iterates over the file for you.

3. Append mode ' A ': The file does not exist then add if the file exists and the file content is appended at the end.

RB: Read
F=open (' aaaa.py ', ' RB ')
Print (F.read (). Decode (' Utf-8 '))

F=open (' 1.jpg ', ' RB ')
Data=f.read ()

WB: Write
F=open (' 2.jpg ', ' WB ')
F.write (data)
F=open (' New_3.txt ', ' WB ')
F.write (' aaaaa\n '. Encode (' Utf-8 '))

WB: Append Write
F=open (' new_3.txt ', ' AB ')
F.write (' aaaaa\n '. Encode (' Utf-8 '))

Context Management:

  with open (' aaaa.py ', ' R ', encoding= ' Utf-8 ') as read_f,\ 
 Open (' aaaa_new.py ', ' W ', encoding= ' utf-8 ') as writ E_f: 
 Data=read_f.read () 
 Write_f.write (data) 
 
 
 loops through each line of content 
 with open (' A.txt ', ' R ', encoding= ' Utf-8 ') as F: 
 while True: 
 Line=f.readline () 
 If not line:break 
 print (line,end= ")  
 Lines=f.readlines () #只适用于小文件 
 Print (lines) 
 
 Data=f.read () 
 Print (type data) 
 
 
 For line in F: #推荐使用 
 Print (line,end= ') 
  

Modification of files
Mode One: Applies only to small files
Import OS
With open (' A.txt ', ' R ', encoding= ' Utf-8 ') as read_f,\
        Open (' A.txt.swap ', ' W ', encoding= ' Utf-8 ') as Write_f:
    Data=read_f.read ()
    Write_f.write (Data.replace (' alex_sb ', ' ALEX_BSB '))

Os.remove (' A.txt ')
Os.rename (' A.txt.swap ', ' a.txt ')


Way two:
Import OS
With open (' A.txt ', ' R ', encoding= ' Utf-8 ') as read_f,\
        Open (' A.txt.swap ', ' W ', encoding= ' Utf-8 ') as Write_f:
    For line in Read_f:
        Write_f.write (Line.replace (' ALEX_BSB ', ' BB_ALEX_SB '))

Os.remove (' A.txt ')
Os.rename (' A.txt.swap ', ' a.txt ')

Python diary----2017.7.24