handling unexpected exceptions in pdb

Simon Bierbaum bierbaum at vierfalt.com
Thu Jul 10 17:12:36 EDT 2008

Am 10.07.2008 um 20:52 schrieb R. Bernstein:

> Simon Bierbaum <bierbaum at vierfalt.com> writes:
>> Hi all,
>> I'm in an interactive session in pdb, debugging my code using
>> pdb.runcall. Somewhere, an exception is raised and lands uncaught on
>> stdout. Is there any way of picking up this exception and at least
>> read the full message, or even accessing its stack trace to determine
>> where exactly within the one line I just executed it was raised? This
>> is where I'm stuck:
>>> /usr/local/apache2/bin/Model/Database.py(287)disconnect()
>> (Pdb) n
>> FlushError: FlushErr...perly.",)
>>> /usr/local/apache2/bin/Model/Database.py(287)disconnect()
>> (Pdb) import sys
>> (Pdb) sys.last_traceback
>> *** AttributeError: 'module' object has no attribute 'last_traceback'
>> Thanks, Simon
> I think basically you want runcall to be wrapped in a try block. So  
> in pdb.py
> instead of:
> def runcall(*args, **kwds):
>     return Pdb().runcall(*args, **kwds)
> Change with:
> def runcall(*args, **kwds):
>     p=Pdb()
>     try:
>       return p.runcall(*args, **kwds)
>     except:
>       traceback.print_exc()
>       print "Uncaught exception. Entering post mortem debugging"
>       t = sys.exc_info()[2]
>       p.interaction(t.tb_frame,t)
>       print "Post mortem debugger finished."
>       return None
> Code like this appears near the bottom of the pdb.py file. If that
> works, you may want to file a bug Python report to change pdb. Also
> note that one may want to do the same thing on run() and runeval()
> But also if this does what you want, please file a feature request  
> to pydb:
>   http://sourceforge.net/tracker/?func=add&group_id=61395&atid=497162
> and I'll probably make it happen in the next release.
> This is the first time I've heard of anyone using runcall.

My app is called from mod_python with the PythonEnablePdb option set  
to On, which makes mod_python call my handler function not directly,  
but wrapped into a pdb.runcall(). I figure I might not be the first  
one to use runcall under these circumstances ;-)

I'll definitely give your hack a try, thank you for your help!

Cheers, Simon

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