text: from __future__ import print_function
  import time, os, sys
  import transposition_cipher as transCipher
  
  def main():
      inputFile = 'Prehistoric Men.txt'
      outputFile = 'Output.txt'
      key = int(input('Enter key: '))
      mode = input('Encrypt/Decrypt [e/d]: ')
  
      if not os.path.exists(inputFile):
          print('File %s does not exist. Quitting...' % inputFile)
          sys.exit()
      if os.path.exists(outputFile):
          print('Overwrite %s? [y/n]' % outputFile)
          response = input('> ')
          if not response.lower().startswith('y'):
              sys.exit()
              
      startTime = time.time()
      if mode.lower().startswith('e'):
          content = open(inputFile).read()
          translated = transCipher.encryptMessage(key, content)
      elif mode.lower().startswith('d'):
          content = open(outputFile).read()
          translated =transCipher .decryptMessage(key, content)
  
      outputObj = open(outputFile, 'w')
      outputObj.write(translated)
      outputObj.close()
      
      totalTime = round(time.time() - startTime, 2)
      print(('Done (', totalTime, 'seconds )'))
      
  if __name__ == '__main__':
      main()
  