This issue tracker has been migrated to GitHub, and is currently read-only.
For more information, see the GitHub FAQs in the Python's Developer Guide.

Author gvanrossum
Recipients abarnert, gvanrossum, martin.panter, ncoghlan, r.david.murray, serhiy.storchaka
Date 2016-01-04.19:22:04
SpamBayes Score -1.0
Marked as misclassified Yes
Message-id <1451935324.29.0.840363611808.issue25958@psf.upfronthosting.co.za>
In-reply-to
Content
I propose to solve the narrow problem by indeed supporting the setting of certain special methods to None similar to __hash__. This should be limited to those methods for which this adds value, e.g. where the complete absence of the method causes a fall-back to a different API (e.g. __getitem__+__len__ in the case of __reversed__) -- the None value should just block the fallback. This will require some changes in the ABCs that test for the presence of a given method (Iterable/__iter__, Container/__contains__, Reversible/__reversed__ -- the latter ABC should be added) and in implementations such as reversed(), iter() and 'in'. Maybe we should just do this for every ABC in collections.abc (plus Reversible) that has a __subclasshook__ that tests for the presence of the special method.

Oh, probably some more, like Iterator/__next__, Sized/__len__ and Callable/__call__. But for those there isn't a fallback in the corresponding bytecode, so I'm only +0 for those -- it doesn't seem to harm anything to be consistent with those for which it does matter, but it doesn't cost much either, and the consistency is slightly useful -- it provides a pattern to follow for future ABCs.
History
Date User Action Args
2016-01-04 19:22:04gvanrossumsetrecipients: + gvanrossum, ncoghlan, r.david.murray, martin.panter, serhiy.storchaka, abarnert
2016-01-04 19:22:04gvanrossumsetmessageid: <1451935324.29.0.840363611808.issue25958@psf.upfronthosting.co.za>
2016-01-04 19:22:04gvanrossumlinkissue25958 messages
2016-01-04 19:22:04gvanrossumcreate