(Twenty-three) Python 3 file operations

File Handling Process

1. Open the file, get the file handle and assigned to a variable
2. Operate on files handles
3. Close the file

Open the file, there are three modes:

• Read-only mode (default)
• Write-only mode (unreadable, you create does not exist, then there is coverage)
• Append mode (read, does not exist is created, only the presence of the additional content)

"+" Indicates a file can be read and written simultaneously: 
1. writable + R & lt file (readable, writable, can be added) 
2. W + W R 
3. a + additional 

"U" indicates the time of reading can be \ r \ r \ n autochanger \ n to \ n (r or r + using the simultaneous mode) 
because the system is Windows newline \ r \ n, newline Linux system is \ n, U is able to automatically add \ r \ n is converted into \ n- 
1. rU 
2. the U-R & lt + 

"B" represents the binary 
1.rb 
2.WB 
3.ab

 

File operations Basic Usage

Basic usage: open ()

= Open the file_object (file_name, access_mode = 'R & lt', Buffering = -1) 

        Open function has many parameters commonly used file_name, mode and encoding 
        file_name: open the file name, if not the current path is to be noted that the specific path 
        access_mode file open mode 
        buffering may have a value of 0, 1,> 1 three, 0 for off buffer (only available in binary mode), Line 1 represents a buffer (for text mode only),> 1 indicates buffer size initialization;  
        encoding represents the returned data is encoded using what is generally used utf8 or GBK;

　

# File Open Open () 
F = Open ( 'test.txt', 'R & lt +') 
# or with open () after the completion of this method of operation, will automatically turn off unneeded Close () 
with Open ( 'test.txt', 'R & lt') AS F: 
   reached, f.read () 


# close the file 
F = Open ( 'test.txt', 'R & lt +', encoding = 'UTF-. 8') 
RET = reached, f.read () 
Print (RET) 
F. Close () 


# read the contents of the file (to specify each read word character) 
F = Open ( 'test.txt', 'R & lt +', encoding = 'UTF-. 8') 
RET reached, f.read = (. 8) 
Print ( RET) 



# reads data (read may specify the number of characters), stored as a display list 
F = Open ( 'test.txt', 'R & lt +', encoding = 'UTF-. 8') 
RET = f.readlines () 
Print ( RET) 
f.close () 



# read data line 
F = Open ( 'test.txt', 'R & lt +', encoding = 'UTF-. 8') 
RET = F.readline()
print(ret)
f.close()


 
# write to file write () argument is a string
Open = F ( 'test.txt', '+ A', encoding = 'UTF-. 8') 
f.write ( "ABC") 
RET = reached, f.read () 
Print (RET) 
f.close () 



# write files , the writelines () is a sequence of parameters, such as a list, it will help you to write the file iteration 
F = Open ( 'test.txt', '+ A', encoding = 'UTF-. 8') 
f.writelines ([ "AA", "BB", "CC"]) 
RET = reached, f.read () 
Print (RET) 
f.close () 



# determines whether the file is a unified tty device 
f = open ( 'test.txt', 'r +', encoding = ' . 8-UTF ') 
RET = f.isatty () 
Print (RET) #False 
f.close () 



# determines whether or not readable (unreadable error is "No File or Directory SUCH:") 
F = Open (' test.txt ',' R & lt + ', encoding =' UTF-. 8 ') 
RET = F.readable's () 
print (ret) #True 
f.close () 



# specified file position of the pointer  
f = open ( 'test.txt', 'r +', encoding = 'utf-8')
ret = f.read (8) # 8 characters first read 
print (ret)
f.seek (0) # and then move the pointer to the beginning of the file 
ret = f.read (8) # reread 
Print (RET) 
f.close () 



# Get pointer position 
f = open ( 'test.txt' , 'R & lt +', encoding = 'UTF-. 8') 
RET reached, f.read = (. 8) # 8 characters first read 
print ( "pointer position:% s "% f.tell ()) # Check current pointer position 
print (RET) 
f.seek (0) # reset to the start position designated 
print ( "pointer position:% s "% f.tell ()) # viewing the pointer position 
f.close () 



# truncate data file, retaining only before data (number of bytes specified) 
F = Open ( 'test.txt', 'R & lt +', encoding = 'UTF-. 8') 
f.truncate (. 8) # file keeping only the first 8 bytes of data, later in the file delete all the data 
RET = f.read () 
Print (RET) 
() f.close 



# file descriptor 
f.fileno () 



inside # refresh file buffer 
f.flush ()