[Python-ideas] A (meta)class algebra

[Thomas Kluyver]

On 12 February 2015 at 05:42, Martin Teichmann <lkb.teichmann at gmail.com>
wrote:

> With my addition, one could simply add a method
> to MetaRegistrar:
>
> def __add__(self, other):
>     class Combination(self, other):
>         pass
>     return Combination
>

Having recently had to refactor some code in IPython which used multiple
inheritance and metaclasses, -1 to this idea.

1. More magic around combining metaclasses would make it harder to follow
what's going on. Explicit (this has a metaclass which is a combination of
two other metaclasses) is better than implicit (this has a metaclass which
can combine itself with other metaclasses found from the MRO).
2. I *want* it to be hard for people to write multiple-inheriting code with
multiple metaclasses. That code is most likely going to be a nightmare for
anyone else to understand, so I want the person creating it to stop and
think if they can do it a different way, like using composition instead of
inheritance.

Thomas
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