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

Terry Reedy tjreedy at udel.edu
Sun Sep 22 01:55:05 CEST 2013

On 9/21/2013 6:15 PM, R. David Murray wrote:
> On Sat, 21 Sep 2013 17:16:41 -0400, Terry Reedy <tjreedy at udel.edu> wrote:
>> When an AttributeError is raised in a __del__ method, it is caught and
>> ignored, except that it is not completely ignored but is replaced by a
>> warning message sent to stderr. Example:
>>   >>> class C():
>> 	def __del__(self): raise AttributeError
>>   >>> c=C()
>>   >>> del c
>> Exception AttributeError: AttributeError() in <bound method C.__del__ of
>> <__main__.C object at 0x000000000351A198>> ignored
> This is a replacement for a traceback.  In later Python versions, the
> full traceback is printed.

The above is 3.3.2. In 3.4.0a2, the traceback of the ignored exception 
is indeed printed.

Exception ignored in: <bound method C.__del__ of <__main__.C object at 
Traceback (most recent call last):
   File "<pyshell#0>", line 2, in __del__

> In the general case it represents a bug in
> the code that should be fixed.  Most such errors arise from the vagaries
> of module finalization (such as your issue 19021),

Lets call that a buglet ;-). Not really harmful, but annoying. Accepting 
that even such buglets 'should' be fixed in the stdllib, so that the 
message does not appear, is there any reason *not* to make it a 
RuntimeWarning so that users who care about clean output can filter it 
out while waiting for us to fix it?

This would be a separate issue from #12085.

 > but not all of them
> do: the rest represent real bugs in __del__ methods (which are executed
> asynchronously in the general case).

Which is why the message should be printed, so the developer can decide.

Terry Jan Reedy

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