getting special from type, not instance (was Re: [Python-Dev] copy confusion) (original) (raw)

Phillip J. Eby pje at telecommunity.com
Thu Jan 13 15:41:31 CET 2005

At 10:16 AM 1/13/05 +0000, Armin Rigo wrote:

On the other hand, I fear that if there is a standard "metamethod" decorator (named after Phillip's one), it will be misused. Reading the documentation will probably leave most programmers with the feeling "it's something magical to put on methods with _ in their names",

Possible solution: have it break when it's used in a non-subtype of 'type'. That is to say, when it's not used in a metaclass.

Finally, I wonder if turning all methods whatsoever into data descriptors (ouch! don't hit!) would be justifiable by the feeling that it's often bad style and confusing to override a method in an instance (as opposed to defining a method in an instance when there is none on the class).

Hm. I look at this the opposite way: sometimes it's nice to provide a default version of a callable that's supposed to be stuck on the object later, just like it's nice to have a default initial value for a variable supplied by the type. I don't think that doing away with this feature for non-special methods is a step forwards.

In all cases, I'm +1 on seeing built-in method objects (PyMethodDescrType) become data descriptors ("classy descriptors?" :-).

Heh. :)

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