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

[Walter Dörwald]

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
>>re-raised?
> 
> 
> (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?

Bye,
    Walter Dörwald