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[Python-Dev] Reference cycles in Exception.__traceback__

Antoine Pitrou solipsis at pitrou.net
Thu Mar 6 16:52:56 CET 2014 
Le 06/03/2014 16:03, Yury Selivanov a écrit :
>
> On 2014-03-06, 8:42 AM, Antoine Pitrou wrote:
>> Le 05/03/2014 23:53, Nick Coghlan a écrit :
>>>
>>> __traceback__ wouldn't change [...]
>>
>> Uh, really? If you want to suppress all reference cycles, you *have*
>> to remove __traceback__.
>>
>> The problem is to make computation of the traceback summary
>> lightweight enough that it doesn't degrade performance in the common
>> case where you don't have to print the traceback later.
>
> So why can't we allow instantiation of types.TracebackType &
> types.FrameType?

IMO it is absolutely out of question to allow creation of arbitrary 
frames from Python code, because the structure and initialization of 
frames embody too many low-level implementation details.

We might allow the creation of traceback objects, but without any custom 
frame objects it is unclear how useful that would be.

Regards

Antoine.
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