[Python-Dev] Should issubclass() be more like isinstance()?

Wed Apr 5 22:31:10 CEST 2006

Crutcher Dunnavant wrote:
> On 4/4/06, Greg Ewing <greg.ewing at canterbury.ac.nz> wrote:
>> Crutcher Dunnavant wrote:
>>> B) issubclass() won't work on a list of classs,
>> > the way isinstance() does.
>>>> That sounds more reasonable. I can't think of any
>> reason why it shouldn't work.

There is an issue of confusion:
 class CheeseShop(Sketch, ByCleese, ByGraham): pass
You need to be careful that the user understands
 issubclass(SillyWalks, (Sketch, ByCleese, ByGraham))
is not simply testing that SillyWalks has the same ancestors as
CheeseShop, but is True simply because issubclass(SillyWalks, Sketch)
is True. More a document issue than anything, but to be considered.
--Scott David Daniels
Scott.Daniels at Acm.Org