[Python-Dev] Mutable exceptions? (was Re: PEP 293, Codec Error Handling Callbacks)

Walter Dörwald walter@livinglogic.de
Fri, 16 Aug 2002 10:27:17 +0200

Guido van Rossum wrote:

>>This looks like an issue that potentially deserves more community
>>feedback, so I'm ripping it out and starting a new thread: should
>>exception objects be treated as mutable as exceptions get caught and
> (A new thread in python-dev hardly counts as "community feedback".)
> I'd say definitely.  Code like this looks reasonable to me:
>   def some_function(arg):
>     try:
>       call_some_other_function(arg)
>     except SomeExpectedExceptionClass, obj:
>       obj.add_context(arg)
>       raise
> Then some outer piece of code catches exceptions and produces a
> traceback augmented by information added by various calls to
> add_context().

So, if add_context() changes any exception attribute that was
originally specified in the constructor and is thus part of
the args attribute, should this change be reflected in the
args attribute?

    Walter Dörwald