python_ file processing

One, character encoding

1. The memory is fixed using unicode encoding
2. The data is first generated in the memory in the unicode format, if you want to transfer it needs to be converted to bytes format

# unicode -------> enconde( u t f - 8 ) -------> bytes

Get the bytes, you can store it in a file or transfer it over the network

# bytes --------> enconde( u t f - 8 ) -------> unicode

1. Strings are recognized as unicode in Python 3

String encode in Python 3 gets bytes

Strings in Python 2 are bytes

Python 2 add'u' before the string, which is unicode

2. File processing

Process: Open the file ===> get the file handle and assign it to the variable ====> manipulate the file through the handle ==> close the file

Read the file:

1 f =open( ‘aaaa.py ’ , ‘ r ’ ,encoding = ‘utf-8’ )23print( f.readline(),end= ‘’)#Read a line
 45 print( f.readlines(), end=’’ )#Read all, no line break
 67 print( f.readable())#Readable file
 89 print( f.writable())#Unwritable file
1011 f.close()#It must be closed after the end, otherwise it will occupy memory

Write file:

f =open( ‘new_2’, ‘w’,encoding=’utf-8’ )print( f.readable())#Unreadable

print( f.writable())#Writable

f.write( ‘888888\n’ )#Append single line

f.write( ‘999999\n’ )#Append

f.writelines([ ‘787878\n’ , ‘878787\n’])#Append multiple lines

f.close()#Close file

Append:

f=open('new_2','a',encoding='utf-8')print(f.readable())        #Unreadable

print(f.writable())         #Writable

f.write('888888\n')       #Append single line

f.write('999999\n')

f.writelines(['787878\n','878787\n'])       #Append multiple lines

f.close()

# rb

f=open('aaaa.py','rb')    #Open in bytes

print(f.read().decode('utf-8'))

Copy picture:

f=open('1.jpg','rb')      #Open 1 in rb way.JPG

data=f.read()           #data gets the content of f

print(data)

f2=open('3.jpg','wb')      #Open as write

f2.write(data)         #Write the content of data to f2

f2.close()

f.close()

# ab, append in binary form

f=open('new_3.txt','ab')

f.write('aaaaa\n'.encode('utf-8'))

• Context management:

withopen('aaaa.py','r',encoding='utf-8')as read_f,\

  open('aaaa_new.py','w',encoding='utf-8')as write_f:

 data=read_f.read()

 write_f.write(data)

Take each line of the file in a loop:

withopen('a.txt','r',encoding='utf-8')as f:while True:

  line=f.readline()if not line:breakprint(line,end='')

 
 lines=f.readlines() #Only for small files

 print(lines)
 

 data=f.read()print(type(data))for line in f: #Recommended Use

  print(line,end='')

File modification:

Method 1: Only applicable to small files

1 import os
 23 withopen('a.txt','r',encoding='utf-8')as read_f,\
 45 open('a.txt.swap','w',encoding='utf-8')as write_f:67     data=read_f.read()89     write_f.write(data.replace('alex_SB','alex_BSB'))10111213 os.remove('a.txt')1415 os.rename('a.txt.swap','a.txt')

**# Method 2: **

import os

withopen('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')

File function operation introduction