old_contents: #! python3
  # P09_countdown.py - A simple countdown script.
  #
  # Note:
  # - sound file can be downloaded from http://nostarch.com/automatestuff/
  
  import time, subprocess
  
  timeLeft = 60
  while timeLeft > 0:
      print(timeLeft)
      time.sleep(1)
      timeLeft = timeLeft - 1
  
  # At the end of the countdown, play a sound file.
  subprocess.Popen(['see', 'alarm.wav'])
  
new_contents: #! python3
  # P09_countdown.py - A simple countdown script.
  #
  # Note:
  # - sound file can be downloaded from http://nostarch.com/automatestuff/
  
  import time, subprocess
  
  timeLeft = 60
  while timeLeft > 0:
      print(timeLeft)
      time.sleep(1)
      timeLeft -= 1
  
  # At the end of the countdown, play a sound file.
  subprocess.Popen(['see', 'alarm.wav'])
  
subject: Update P09_countdown simplified subtraction expression