I'm with Raymond. Metaclasses that don't derive from 'type' can create objects that are neither fish nor flesh.
After thinking this through some more, I have to retract that. After all, even classic classes and their instances are derive from object:
class C: pass
isinstance(C, object) True
isinstance(C(), object) True
Hmm, that surprises me. After all, writing class C(object): pass makes it new-style. Also dir(C()) or dir(C) does not show any of the methods given by dir(object) or dir(object()).
What makes a classic class is one very specific metaclass. What makes a classic instance is a class using that very specific metaclass. Everything else is a new-style class.
While true, I think it more pragmatic to have the docs and terminology *not* expressed in terms of meta-classes; rather, it is simpler to focus on the distinction between class C and class C(object), noting that all the new gizmos only work with the latter. The theory is simple, one shouldn't have to understand meta-classes in order be able to use property, classmethod, staticmethod, super, __slots__, __getattribute__, descriptors, etc. Practically, in all code that doesn't explicitly create meta-classes, the sole trigger between new and old is adding object, list, or other builtin type as a base class. IOW, I think the docs ought to continue using wording like this for property: "Return a property attribute for new-style classes (classes that derive from object)." There would be much loss of clarity and understanding with wording like: "Return a property attribute for a class whose metaclass is type or that implements the class semantics of type.__getattribute__ and the instance semantics of object.__getattribute__." For purposes of my article on descriptors, I'll continue with the current approach of ignoring meta-classes. There is enough information presented that meta-class writers will quickly understand why all the new-style gizmos stopped working when they didn't carry forward the semantics of object.__getattribute__ and type.__getattribute__. I think all of the topics are best understood in terms of three groups: classic classes, new-style classes, and roll your own classes. Lumping the latter two together won't help one bit. 'nuff said, Raymond Hettinger ################################################################# ################################################################# ################################################################# ##### ##### ##### ################################################################# ################################################################# #################################################################