[Python-Dev] Should we do away with unbound methods in Py3k? (original) (raw)

Guido van Rossum guido at python.org
Fri Nov 23 05:19:57 CET 2007

It looks like we're in agreement to drop unbound methods and have a reasonable set or arguments around it (e.g. keep staticmethod, no changes to methods of builtin types, etc.). Do we need a PEP? It's essentially a 2-line change in funcobject.c (func_descr_get()) -- plus fixing up half a dozen or so unittests that specifically seem to test the behavior of unbound methods.

--Guido

On Nov 22, 2007 6:14 PM, Phillip J. Eby <pje at telecommunity.com> wrote:

At 01:14 PM 11/23/2007 +1300, Greg Ewing wrote: >Guido van Rossum wrote: > > Not quite. You can evolve an API from an instancemethod into a > > staticmethod without changing the call sites. > >But is there ever any need to do that, rather than leave >it as an instance method?

Yes. :) See below.

>Personally it would never have occurred to me to do that. >If you want to be able to override it in subclasses, to >me that's an indication that it should be an instance >method. Or a classmethod, or a staticmethod. The most common use case for this (in my experience) is when you need a converter function or some other sort of function that's configurable per-instance or per-subclass. If you are configuring it per-class and accessing it per-instance, and reusing an existing function, you have to make it a staticmethod. >Also, what happens if you perform such a migration and >then some subclasser later finds that he wants access to >'self'? Then he overrides it with a normal method.

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-- --Guido van Rossum (home page: http://www.python.org/~guido/)

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