If code is waiting on a wait_variable at program exit then the program never fully exits. The command prompt never returns and the process doesn't seem to be doing much of anything (i.e. no heavy CPU usage). ctrl-C has no effect.

I have found that binding to <Detroy> does work around the problem.

I saw this using a unix/X11 build of Python 2.3.4 on MacOS X 10.3.4 and also the standard Python 2.3 framework build included with MacOS X 10.3.

The attached file gives a good example. To see the problem, execute the script and then close the root window before the script finishes (you have 10 seconds).