How to troubleshoot hanging script?

[Alexandru Palade]

Hi,

Just a thought, I'm not sure it's the best way.
You can start an alarm just before the line you *think* it's wrong and
cancel it after that. If it's activated then you probably have
pinpointed the location. Have a look at the signals module
http://docs.python.org/lib/module-signal.html, the alarm function.

Hope it helps.

kj wrote:
> Hi!  I have a Pythonoob question.
>
> I have a script that hangs indefinitely at random times; the only
> thing to do at this point is to kill it.
>
> I'm looking for suggestions on how to troubleshoot and debug the
> problem.
>
> I'm not even sure of where exactly the script is hanging, though
> I suspect it is right around when it tries to read from a pipe
> (generated by popen).  (I arrived at this guess by putting print
> statements all over the place, but I'm not sure this is a very
> reliable way to pinpoint the error.)
>
> So the first thing I'd like to do is find out exactly where the
> script is hanging.  It would be nice if I could just hit Ctrl-C
> (which sends SIGINT from the terminal) when the script is hanging,
> to kill it and get a backtrace, but when this script hangs it
> becomes unresponsive to Ctrl-C!  The only way to kill it is with
> something like
>
>   % pkill -KILL my_script.py
>
> or even
>
>   % pkill -TERM my_script.py
>
> ...or -ABRT or -QUIT.  I tried to exploit this by adding this to the
> script:
>
> import signal
>
> def term_handler(signum, frame):
>     raise KeyboardInterrupt
>
> signal.signal(signal.SIGTERM, term_handler)
>
> ...but this did not help at all; in fact, after this addition, the script
> no longer responded to pkill -TERM.
>
> TIA!
>
> Kynn
>