On Fri, 10 Jun 2011 11:01:41 -0600, Eric Snow wrote: > On Fri, Jun 10, 2011 at 10:47 AM, Steven D'Aprano > <steve+comp.lang.pyt...@pearwood.info> wrote: >> Here's some Python 3 code that uses a factory function as a metaclass >> to inherit docstrings. Give the class a docstring of an empty string, >> and it will be inherited from the first superclass found with a >> non-empty docstring. >> >> >> > Yeah, the idea of an empty docstring to trigger docstring inheritance > really appeals to me. Nice example. Incidently, aren't metaclasses > always inherited, as opposed to class decorators (which are never)?
Metaclasses are inherited, but the example I give uses a factory function as a metaclass: it manipulates the docstring inside the dict, then returns an ordinary class. That makes it just a fancy class decorator using metaclass syntax. The type of each class A, B, ... F is just type, which means that when you subclass each class you don't get any magic metaclass behaviour unless you explicitly set the metaclass directly. That is: assert type(A) is type succeeds, so class B(A) doesn't do anything special unless you explicitly set the metaclass. I followed up with a second example using a conventional metaclass, that is, where the type of each class is *not* type. In that case, the magic behaviour is inherited and there's no need to explicitly set the metaclass except for the first time. (Whew. Talking about metaclasses is hard work.) -- Steven -- http://mail.python.org/mailman/listinfo/python-list
