Python Learning (11) files and streams

11.1 Open File

>>> f = open (R ' C:\text\somefile.txt '), the first parameter is the file name, must have, the second is the pattern, and the third parameter is the buffer.

　11.1.1 file Mode

　　If the open function takes only one filename parameter, then we can get the file object that can read the contents of the file. If you want to write content to a file, you must provide a schema parameter

' r '-----read mode (the same as the effect of non-enactment)

' W '-----write mode

' A '-----append mode

' B '-----binary mode (Python assumes that all the text files (including characters) are processed, but if it is a different type of file (binary), such as a sound or an image, specify B mode)

( why binary mode: \ n and \ r \ n are converted, but if it is a binary file, it will not go.) )

' + '-----read/write mode

11.1.2 Buffering

If it is 0 (False), I/O is unbuffered, and all read and write operations are directed against the hard disk;

If it is 1 (True), it is buffered, using memory instead of the hard disk, the speed is fast, only when flush or close to update the data on the hard disk.

Greater than 1, which represents the buffer size (in bytes), 1 represents the use of the default buffer size.

11.2 Basic File methods

　11.2.1 Read and Write

>>> f = open (R'c:\text\somefile.txt','w')      Write >>> f.write ('ABCD \ r \ n gh')15>>> F.flush ()                                  //  call Close () or flush () to actually write it in

>>> F=open (R ' C:\text\somefile.txt ', ' r ')//Read
>>> F.read (4)//Read Only 4
' ABCD '

>>> f.read ()//Read all
' \ n EF \ n gh '

11.2.2-Tube output

　　The output of the previous command is the input to the next command, with the symbol "|" Connection

11.2.3 Read-write line

>>> f.readline ()  ' >>> f.seek (0)   //   Navigate to text start 0 >>>
   
     f.readline ()   //Read a line  
    '
    ABCD \ n
    ' >>>
     f.readlines ()  //Read the Some rows, return list [
    ' 
     EF \ n
    
    '
    \ n
    '
     
     gh  
    ']
    
        
    
F.writelines ([' AfA ', ' GDF ', ' GFDG '])  //write the list by line
   

11.2.4 Closing files

　　The file operation should, in Finally, call F.close (), so that the exception can also be properly closed file.

11.2.5 using the basic file method

11.3 Iterating over the contents of a file

　11.3.1 Processing by byte　

f == f.read (1) while char:    process (char)    = f.read (1) F.close ()

11.3.2 row-by-line operation

　　 ReadLine ()

11.3.3 Read all content

　Read (): The Read method without parameters can read all rows.

ReadLines (): reads all rows.

11.3.4 using Fileinput to implement lazy line iterations

　　ReadLine () reads one line at a time.

Import Fileimput  for inch fileinput.input (filename):    process (line)

11.3.5 File iterator

f = open (filename) for in F:    processs (line) f.close ()

Python Learning (11) files and streams