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()
  