Appending to a file

Whenever a file is opened using the write flag w, the contents of the file are deleted and opened afresh to write data. There is an alternative flag a that enables appending data to the end of the file. This flag also creates a new file if the file (that is passed as an argument to open) doesn't exist. Let's consider the code snippet below where we append a line to the text file write_file.txt from the previous section:

if __name__ == "__main__": 
   # open text file to append
   file = open('write_file.txt', 'a') 
   # append a line from the file
   file.write('This is a line appended to the file\n') 
   file.close() 

   file = open('write_file.txt', 'r') 
   data = file.read() 
   print(data) 
   file.close()

When the preceding code snippet is executed (available for download along with this chapter—append_to_file.py), the string This is a line appended to the file is appended to the end of the text of the file. The contents of the file will include the following:

    I am excited to learn Python using Raspberry Pi Zero
    This is a line appended to the file