Multi Heritage with slots

[Eric Brunel]

On Wed, 05 Sep 2007 11:01:56 +0200, Alexandre Badez  
<alexandre.badez at gmail.com> wrote:

> Hye,
>
> I'm developing a little app, and I want to make multi heritage.
> My problem is that my both parent do have __slots__ define.
>
> So I've got something like:
>
> class foo(object):
>     __slots__ = ['a', 'b']
>     pass
>
> class foo2(object):
>     __slots__ = ['c', 'd']
>     pass
>
> class crash(foo, foo2):
>     pass
>
> If you write only that in a sample file or in python console (as I
> did), python refuse to load the module and report something like:
>
> Traceback (most recent call last):
>   File "<stdin>", line 1, in ?
> TypeError: Error when calling the metaclass bases
>     multiple bases have instance lay-out conflict
>
> Do you know why it append? And how could I make this work?

See http://mail.python.org/pipermail/python-list/2006-December/418768.html

Basically, the general advice you're likely to get here is: don't use  
__slots__, or at least don't use __slots__ with inheritance.

BTW, what are you trying to do? Is it really a memory footprint  
optimization, which is the intended use case for __slots__, or are you  
just doing Java in Python?
-- 
python -c "print ''.join([chr(154 - ord(c)) for c in  
'U(17zX(%,5.zmz5(17l8(%,5.Z*(93-965$l7+-'])"