[Python-Dev] Revert #12085 fix for __del__ attribute error message

Nick Coghlan ncoghlan at gmail.com
Mon Sep 23 05:24:56 CEST 2013

On 23 Sep 2013 06:38, "Terry Reedy" <tjreedy at udel.edu> wrote:
> On 9/22/2013 2:41 PM, Guido van Rossum wrote:
>> On Sun, Sep 22, 2013 at 10:35 AM, Terry Reedy <tjreedy at udel.edu
>> <mailto:tjreedy at udel.edu>> wrote:
>>     On 9/21/2013 10:30 PM, Guido van Rossum wrote:
>>         Exceptions in __del__ point to bugs (sometimes in the stdlib)
>>         should be fixed, period. The only reason they do not result in
>>         exceptions that are properly bubbled up and catchable is because
>>         __del__
>>         is called from a DECREF macro which has no return value.
>>     That is clear enough. What fooled me is the word 'ignored', in both
>>     the doc and message. How about 'skipped' (for technical reasons)?
>> That's a good point, although I'm not sure 'skipped' is better.
> Only slightly ;-). The problem with both words is that they try to say
two things. What happened, and what Python did about it.
>> Maybe use a more neutral verb like 'occurred'?
> "Exception occurred in ..." is even better at say what happened.
> I think we should then add an explict statement as to what Python did,
and hint at what the user should do, something like
> "Although caught internally, it still indicates a problem."

Brevity is still a virtue. The relevant C API function is called
"PyErr_WriteUnraisable", so just starting the message as something like
"Unraisable exception suppressed in..." might work.


> Otherwise, when no other output follows, as in
> ...
> > del c
> Exception ocurred in: <bound method C.__del__ ...
> Traceback (most recent call last):
>   File "<pyshell#0>", line 2, in __del__
> AttributeError:
> >>>
> It may not be completely obvious to a non-expert that the traceback is
not a 'real' traceback from an exception that was allowed to propagate, and
that it did not stop execution and cannot be caught.
> --
> Terry Jan Reedy
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