[Python-3000] Metaclasses in Python 3000: Draft 2

[Jack Diederich]

On Wed, Mar 14, 2007 at 12:29:09AM -0700, Talin wrote:
>      # The metaclass
>      class OrderedClass(type):
> 
>          # The custom dictionary
>          class member_table(dict):
<snip>

I would move the member_table class out of the OrderedClass namespace so
no one gets any funny ideas that it has to be nested.

> Alternate Proposals
>
>      Another good suggestion was to simply use an ordered dict for all
>      classes, and skip the whole 'custom dict' mechanism. This was based
>      on the observation that most use cases for a custom dict were for
>      the purposes of preserving order information. However, this idea has
>      two drawbacks, first because it means that an ordered dict
>      implementation would have to be added to the set of built-in types
>      in Python, and second because it would impose a slight speed (and
>      complexity) penalty on all class declarations.

FYI, I did a hacky implementation to test speed by making a copy of
dictobject.c and storing key names in a PyList on the object.  The slowdown
for inserting 100k unique keys (/usr/share/dict/words) was 10%.  There
was no appreciable slowdown for lookup (it uses the normal hash lookup).
I didn't implement deletion so I don't know how much it would suffer.

-Jack