On 7/22/06, Andrew Koenig <[EMAIL PROTECTED]> wrote: > This example illustrates an important point: Some object properties don't > correspond directly to the presence of a particular attribute, and can't > easily be made to do so. > > In other words: > > Is it callable? No problem, just check for __call__ > > Is it iterable? Well, you can't quite check for __iter__ because > some iterable types don't have them. Well, we can fix that problem: > Change those types so that they have __iter__ to signal that they > are iterable. > > Is it hashable? That's a tough question to answer, because you > have to inspect recursively all of the object's components. So > you can't just test for __hash__; you have to call it. > > To my way of thinking, callable, iterable, and hashable are the same kind of > concept, and I wish Python would provide a uniform way of finding out > whether such concepts apply to an object. That uniform way doesn't have to > be in __builtins__, but it would be nice for it to exist.
Hm... Is a uniform API really a good idea for things that have totally different performance characteristics? Computing hashability is about as expensive as computing the hash... -- --Guido van Rossum (home page: http://www.python.org/~guido/) _______________________________________________ Python-3000 mailing list Python-3000@python.org http://mail.python.org/mailman/listinfo/python-3000 Unsubscribe: http://mail.python.org/mailman/options/python-3000/archive%40mail-archive.com
