code: def replace_text(filepath, to_replace, replacement):
          
          with open(filepath) as file:
              s = file.read()
          s = s.replace(to_replace, replacement)
          with open(filepath, 'w') as file:
              file.write(s)
docs: Replaces a string in a given file with another string
  
          :param file: the file in which the string has to be replaced
          :param to_replace: the string to be replaced in the file
          :param replacement: the string which replaces 'to_replace' in the file