First make sure that Python is able to read the path to your file.

 from os import path

 if path.exists('ranks.dat'):
 # do the file processing
 else:
 print('Filepath does not exist.')


In addition, you can also use a `context manager` to open and close the file for you when you are done

 with open('ranks.dat', 'r') as f:
 for line in f.readlines():
 print(line)