python exit infinite while loop with KeyboardInterrupt exception

Question

My while loop does not exit when Ctrl+C is pressed. It seemingly ignores my KeyboardInterrupt exception. The loop portion looks like this:

while True:
  try:
    if subprocess_cnt <= max_subprocess:
      try:
        notifier.process_events()
        if notifier.check_events():
          notifier.read_events()
      except KeyboardInterrupt:
        notifier.stop()
        break
    else:
      pass
  except (KeyboardInterrupt, SystemExit):
    print '\nkeyboardinterrupt found!'
    print '\n...Program Stopped Manually!'
    raise

Again, I'm not sure what the problem is but my terminal never even prints the two print alerts I have in my exception. Can someone help me figure this problem out?

Your first except KeyboardInterrupt catches the exception. It won't be visible to the second except (KeyboardInterrupt, SystemExit) if you don't re-raise it. — eumiro
@eumiro - I commented out the first KeyboardInterrupt and replaced the contents of the exception with 'pass' but I'm still experiencing the same problem. Ctrl+C is being ignored (ps aux shows the process still running as well) — sadmicrowave
@eumiro I've also tried to re-raise the KeyboardInterrupt exception by adding raise KeyboardInterrupt() within the first except KeyboardInterrupt: however I'm still experiencing the same issue. — sadmicrowave

wberry wberry · Accepted Answer · 2011-12-27T15:03:57

Replace your break statement with a raise statement, like below:

while True:
  try:
    if subprocess_cnt <= max_subprocess:
      try:
        notifier.process_events()
        if notifier.check_events():
          notifier.read_events()
      except KeyboardInterrupt:
        notifier.stop()
        print 'KeyboardInterrupt caught'
        raise  # the exception is re-raised to be caught by the outer try block
    else:
      pass
  except (KeyboardInterrupt, SystemExit):
    print '\nkeyboardinterrupt caught (again)'
    print '\n...Program Stopped Manually!'
    raise

The two print statements in the except blocks should execute with '(again)' appearing second.

python exit infinite while loop with KeyboardInterrupt exception

1 Answers