__slots_ and inheritance

[Aahz]

In article <b7340h0r7m at enews1.newsguy.com>,
Alex Martelli  <aleaxit at yahoo.com> wrote:
>
>__slots__ is, essentially, an optimization (in terms of memory
>consumption) intended for classes that are likely to be created 
>in very large numbers: you give up the normal flexibility of
>being able to add arbitrary attributes to an instance, and what
>you gain in return is that you save one dictionary per instance
>(dozens and dozens of bytes per instance -- that will, of course,
>not be all that relevant unless the number of instances that are
>around is at the very least in the tens of thousands).

More than that, because of the way modern computer architectures do
caching, using __slots__ tends to speed up instance attribute access.
This also is an optimization, but it's effective with even hundreds of
instances, if you're rapidly switching between instances.
-- 
Aahz (aahz at pythoncraft.com)           <*>         http://www.pythoncraft.com/

This is Python.  We don't care much about theory, except where it intersects 
with useful practice.  --Aahz, c.l.py, 2/4/2002