[Python-Dev] weak refs in descriptors (http://bugs.python.org/issue17950)

Mon May 13 15:20:40 CEST 2013

On Mon, May 13, 2013 at 1:49 PM, Kristján Valur Jónsson
<kristjan at ccpgames.com> wrote:
> Hello python-dev.
>> I‘m working on a patch to remove reference cycles from heap-allocated
> classes: http://bugs.python.org/issue17950
>> Part of the patch involves making sure that descriptors in the class
> dictionary don’t contain strong references to the class itself.
>> This is item 2) in the defect description.
>> I have implemented this via weak references and hit no issues at all when
> running the test suite.
>> But I’d like to ask the oracle if there is anything I may be overlooking
> with this approach? Any hidden problems we might encounter?
>>>> K

Hi Kristjan
The strong reference there is a feature. Descriptors keep the class
alive if somehow the class disappears and the descriptor itself does
not. Please don't change language semantics (yes, this is a change in
semantics), just because the test suite passes - I can assure you
there are people doing convoluted stuff that expect this to work.
Cheers,
fijal