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      Write to File

      Python Tutorial

      This Python tutorial has been written for the beginners to help them understand the basic to advanced concepts of Python Programming Language. After completing this tutorial, you will find yourself at a great level of expertise in Python, from where you can take yourself to the next levels to become a world class Software Engineer.

      Write to File

      To write data to a file in Python, you need to open a file. Any object that interacts with input and output steam is called File object. Python's built-in function open() returns a file object.
      fileObject = open(file_name [, access_mode][, buffering])
      After you obtain the file object with the open() function, you can use the write() method to write any string to the file represented by the file object. It is important to note that Python strings can have binary data and not just text.
      The write() method does not add a newline character ('\n') to the end of the string.

      Syntax

      fileObject.write(string)
      Here, passed parameter is the content to be written into the opened file.

      Example

      # Open a file
      fo = open("foo.txt", "w")
      fo.write( "Python is a great language.\nYeah its great!!\n")
      
      # Close opened file
      fo.close()
      The above method would create foo.txt file and would write given content in that file and finally it would close that file. The program shows no output as such, although if you would open this file with any text editor application such as Notepad, it would have the following content 
      Python is a great language.
      Yeah its great!!

      Writing in Binary Mode

      By default, read/write operation on a file object are performed on text string data. If we want to handle files of different other types such as media (mp3), executables (exe), pictures (jpg) etc., we need to add 'b' prefix to read/write mode.
      Following statement will convert a string to bytes and write in a file.
      f=open('test.bin', 'wb')
      data=b"Hello World"
      f.write(data)
      f.close()
      Conversion of text string to bytes is also possible using encode() function.
      data="Hello World".encode('utf-8')

      Appending to a File

      When any existing file is opened in 'w' mode to store additional text, its earlier contents are erased. Whenever a file is opened with write permission, it is treated as if it is a new file. To add data to an existing file, use 'a' for append mode.

      Syntax

      fileobject = open(file_name,"a")

      Example

      # Open a file in append mode
      fo = open("foo.txt", "a")
      text = "TutorialsPoint has a fabulous Python tutorial"
      fo.write(text)
      
      # Close opened file
      fo.close()
      When the above program is executed, no output is shown, but a new line is appended to foo.txt. To verify, open with a text editor.
      Python is a great language.
      Yeah its great!!
      TutorialsPoint has a fabulous Python tutorial

      Using the w+ Mode

      When a file is opened for writing (with 'w' or 'a'), it is not possible to perform write operation at any earlier byte position in the file. Th 'w+' mode enables using write() as well as read() methods without closing a file. The File object supports seek() unction to rewind the stream to any desired byte position.
      Following is the syntax for seek() method 
      fileObject.seek(offset[, whence])

      Parameters

      offset − This is the position of the read/write pointer within the file.
      whence − This is optional and defaults to 0 which means absolute file positioning, other values are 1 which means seek relative to the current position and 2 means seek relative to the file's end.
      Let us use the seek() method to show how simultaneous read/write operation on a file can be done.

      Example

      The following program opens the file in w+ mode (which is a read-write mode), adds some data. The it seeks a certain position in file and overwrites its earlier contents with new text.
      # Open a file in read-write mode
      fo=open("foo.txt","w+")
      fo.write("This is a rat race")
      fo.seek(10,0)
      data=fo.read(3)
      fo.seek(10,0)
      fo.write('cat')
      fo.close()

      Output

      If we open the file in Read mode (or seek the starting position while in w+ mode), and read the contents, it shows
      This is a cat race

      Practice with Online Editor

      Note: This Python online Editor is a Python interpreter written in Rust, RustPython may not fully support all Python standard libraries and third-party libraries yet.
      Remember to save code(Ctrl + S Or Command + S) before run it.