[Python-Dev] Things to Know About Super (original) (raw)

Phillip J. Eby pje at telecommunity.com
Thu Aug 28 20:54:08 CEST 2008

At 05:50 PM 8/28/2008 +0200, Michele Simionato wrote:

On Aug 28, 5:30 pm, "Phillip J. Eby" <p... at telecommunity.com> wrote: > How is that making things easier for application programmers?

We have different definitions of "application programmer". For me a typical application programmer is somebody who never fiddles with metaclasses, which are the realm of framework builders.

Application programmers use frameworks, and sometimes more than one. If they're subclassing from two different frameworks, each using a different metaclass, they will need to also multiple-inherit the metaclass.

This is in fact so annoying that I created a "universal metaclass" in DecoratorTools whose sole function is to delegate metaclass new, init, and call to class-level methods (e.g. class_new, class_call, etc.), thereby eliminating the need to have custom metaclasses for most use cases in the first place. Now, wherever possible, I use that single metaclass in my frameworks, so that there's no need to mix them.

That, IMO, would be a more useful change than getting rid of super(); it would get rid of the explicit metaclass mixing. (It would still not remove the need for co-operative methods, as the class-delegated methods still need to be co-operative for MI to work.)

There are, of course, other ways to create co-operative function calls besides super(), and I've certainly created more a few of them in my time. (E.g. generic function method combination, instancemethod() chains, and next-method-iterators, to name the ones that occur to me right off.) But these are more for cases where super() is wholly inadequate to the purpose, and none are anywhere near as convenient as super().

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