Multiple inheritance and __slots__

[jm.suresh@no.spam.gmail.com]

Simon Brunning wrote:
> On 14 Dec 2006 05:23:33 -0800, jm.suresh at no.spam.gmail.com
> <jm.suresh at gmail.com> wrote:
> > Hi all,
> > >From the google search, it seems its not possible to do the following.
> >
> > >>> class Test1(object):
> > ...     __slots__ = ['a']
> > ...
> > >>> class Test2(object):
> > ...     __slots__ = ['b']
> > ...
> > >>> class Test3(Test1,Test2):
> > ...     __slots__ = ['c']
> > ...
> > Traceback (most recent call last):
> >   File "<stdin>", line 1, in <module>
> > TypeError: Error when calling the metaclass bases
> >     multiple bases have instance lay-out conflict
> >
> > I just want to make sure that I am using only the attributes a,b and c
> > from the instances of Test3 . Is there any other hack that could be
> > done.
>
> Difficulty with subclassing is the price you pay for abusing slots.
> Slots are intended as a performance tweak only, to minimise the memory
> footprint of classes of which you are going to have a great number of
> instances.
>
> In short - don't do that.
OK. But is there any other way to do what __slots__ does as a 'side
effect' i.e. forcing me to think about the list of attributes my class
is going to have upfront and raising error whenever I violate it. IMHO
this is a very good thing to have even if one does not care about
memory.

--
Suresh

>
> --
> Cheers,
> Simon B
> simon at brunningonline.net
> http://www.brunningonline.net/simon/blog/