try except question - serious foo bar question, and pulling my hair out :-)

Gabriel Genellina gagsl-py2 at
Tue Feb 24 09:52:14 EST 2009

En Tue, 24 Feb 2009 11:09:44 -0200, Laszlo Nagy <gandalf at>  

>> It seems impossible to me. The while loop should only exit if  
>> stop_requested becomes set, OR if an exception is raised. However, all  
>> exceptions are cought and logged. But there are no exceptions logged.  
>> And stop_requested is NOT SET. (see the last line in the log).
>> What is happening here?
> It was a bad assumption. Not all exceptions are subclasses of  
> "Exception". In this case, an inner call raised SystemExit(0).

Glad to see you finally found what was happening!

> So be aware. Don't think that this will catch all exceptions:
> try:
>     ???
> except Exception,e:
>    do_with(e)
> Use this instead:
> import sys
> try:
>     ???
> except:
>    e = sys.exc_value
>    do_with(e)

Only at the outermost block on your code, if ever... The fact that some  
exceptions don't inherit from Exception is on purpose -- usually you  
*dont* want to catch (and swallow) SystemExit (nor KeyboardInterrupt, and  
a few more I think)

Gabriel Genellina

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