Python File Handling

Python File Handling Part 3

File handling is one of the important feature in programming languages. Python provides a way to handle(read, write & modify) both text files as well as binary files. This tutorial will cover peek(), write(), writelines(), flush() and close() functions in detail.

➠ There are various functions available in Python for File handling. Click the function to get more detail about that function.

• Open
• Read
• ReadLine
• ReadLines
• Seek
• Tell
• Peek
• Write
• WriteLines
• Flush
• Close

➠ Peek: The peek() function can be used to peek into file content without moving the position of the cursor in the file. This function is only available for files opened in binary mode.

• Example 1:

  
  fileVar = open("/complete_path_to_file/pythonTest.txt", "rb")
  print(fileVar.peek().decode('utf-8'))
  print(fileVar.tell())
  
  Output:  
  Line 1: This is Python File Handling
  Line 2: This is Python File Handling Testing File
  0  #Even after peeking the data, position of cursor is Zero
  

➠ Write: The write() function takes one string parameter which can be used to write data into the file. The write() function returns the number of characters that were written by function(last call) on to file. File can be written multiple times using write() function.

• Example 1:

  
  fileVar = open("/complete_path_to_file/pythonTestWrite.txt", "w")
  fileVar.write('This is Python File Writing')
  fileVar.close()
  
  Output: 
  27
  *******pythonTestWrite.txt content********
  This is Python File Writing
  ******************************************
  

• Example 2: Using multiple write() functions

  
  fileVar = open("/complete_path_to_file/pythonTestWrite.txt", "w")
  fileVar.write('This is Python File Writing')
  fileVar.write('\nThis is Python\'s second File Writing line')
  fileVar.close()
  
  Output: 
  27
  41
  *******pythonTestWrite.txt content********
  This is Python File Writing
  This is Python's second File Writing line
  ******************************************
  

➠ WriteLines: The writelines() function also takes one string(which should have line delimiter) parameter which can be used to write stream of data into the file. The writelines() function returns the number of characters that were written by function(last call) on to file. This works almost similar to the write() function.

• Example 1:

  
  fileVar = open("/complete_path_to_file/pythonTestWritelines.txt", "w")
  file_str='''This is First Line
  This is Second Line
  This is third Line'''
  fileVar.writelines(file_str)
  fileVar.close()
  
  Output: 
  57
  *******pythonTestWritelines.txt content********
  This is First Line
  This is Second Line
  This is third Line
  ***********************************************
  

• Example 2:

  
  file_list =['This is First Line','This is Second Line', 'This is third Line' , 'This is fourth Line']
  fileVar = open("/complete_path_to_file/pythonTestWritelines.txt", "w")
  fileVar.writelines(i+'\n' for i in file_list)
  fileVar.close()
  
  Output: 
  *******pythonTestWritelines.txt content********
  This is First Line
  This is Second Line
  This is third Line
  This is fourth Line
  ***********************************************
  

➠ Flush: The flush() function can be used to flush data from Python temporary memory to file without closing the file. This is helpful for many use cases(such as making file available as soon as it is processed). It is good practise not to store too much data in the Python memory.

• Example 1:

  
  fileVar = open("/complete_path_to_file/pythonTestWrite.txt", "w")
  fileVar.write('This is Python File Writing example for flush()')
  fileVar.flush()
  

➠ Close: The close() function is used to buffer out data onto the file for newly created or modified file. It is good practice to close out files once users are done with operations(read/write) on file.

• Example 1:

  
  fileVar = open("/complete_path_to_file/pythonTestWrite.txt", "w")
  fileVar.write('This is Python File Writing')
  fileVar.close()
  

****Visit File Handling part 1 for more functions