Daniel Stutzbach <dan...@stutzbachenterprises.com> added the comment:
You can't register an old-style class, but many ABCs support duck-typing by implementing __subclasshook__. ABCMeta caches those results and stores a reference to old-style classes, sometimes in _abc_cache and sometimes in _abc_negative_cache. It can't simply return False. I guess that leaves two options: 1) Make old-style classes weak-referenceable and cache the results of __subclasshook__. 2) Refuse to cache old-style classes and call __subclasshook__ every time for old-style classes. Python 2.7a4+ (trunk:79493, Mar 30 2010, 19:19:13) >>> class old_iterable_class: ... def __iter__(self): ... pass ... >>> import collections >>> issubclass(old_iterable_class, collections.Iterable) True ---------- _______________________________________ Python tracker <rep...@bugs.python.org> <http://bugs.python.org/issue2521> _______________________________________ _______________________________________________ Python-bugs-list mailing list Unsubscribe: http://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com
