Python: file operations,

Python: file operations,

Open a file

When operating file 1 to open a file, you need to specify the file path and open mode: r: Read-Only w: Write only a: APPEND "+" indicates that you can read and write a file at the same time r +: read/write w +: Write read a +: Same as

U "indicates that \ r \ n can be automatically converted to \ n (used in the same mode as r or r +) during read)

• RU
• R + U

"B" indicates processing binary files (for example, sending and uploading ISO image files via FTP, which can be ignored in linux and must be noted when processing binary files in windows)

• Rb
• Wb
• Ab1 f = open ('test. log', 'r + ', encoding = 'utf-8') 2 f. write ('sdhgrbfds in saf ') 3 print (f. tell () # view the current pointer position, in the unit of characters 4 f. seek (4) # specify the current pointer position, in bytes 5 print (f. read (4) 6 f. truncate () # Read the data before the pointer 7 print (f. tell () 8 f. close ()View Code

  Ii. Common File Operations

  F = open ('data', 'R') # open in read-only mode (read-only by default)

  F = open('f.txt ', encoding = 'Latin-1') # python3.0 Unicode file

  String = f. read () # read the file into a string

  String = f. read (N) # N Bytes after reading the pointer

  String = f. readline () # Read the next row, including the end identifier of the row

  Alist = f. readlines () # Read the entire file to the string list

  F. write () # write a string to a file

  F. writelines () # Write all strings in the list to a file

  F. close () # manually close

  F. flush () # fl the output buffer to the hard disk.

  F. seek (N) # Move the file pointer to N, in bytes

  for line in open('data'):  

  Print (line) # The file iterator reads a row of the file

  open('f.txt','r').read() #read all at ance into string

  3. Store and parse python objects in files

  X, y, z = 41,42, 43
  S = 'spam'
  D = {'A': 1, 'B': 2} # dictionary object
  L = ['A', 'B', 'C'] # list
  F = open('f.txt ', 'w ')
  F. write (s + '\ n ')
  F. write ('% s, % s, % s \ n' % (x, y, z ))
  F. write (str (D ))
  F. write ('\ n ')
  F. write (str (L ))
  F. close ()
  Print(open('f.txt '). read () # output the File Content
  # Retrieve data from the file and determine its type
  '''
  A = fi. readline ()
  B = fi. readline ()
  C = fi. readline ()
  D = fi. readline ()
  
  Print (a, B, c, d, type (a), type (B), type (c), type (d ))
  '''
  # Retrieve data from the file and convert it to the type before storage
  Fi = open('f.txt ')
  A = fi. readline (). rstrip () # rstrip () Remove the line break
  Print (a, type ())
  B = fi. readline (). rstrip (). split (',') # The split () method of the string. Write a separator in the brackets to split the string into a list.
  Print (B, type (B ))
  C = fi. readline ()
  C = eval (c) # Call the built-in function eval () to convert the string into executable python code.
  Print (C, type (C), type (c ))
  D = fi. readline ()
  D = eval (d)
  Print (D, type (D), type (d ))