On Mon, Jul 30, 2012 at 12:51 PM, Guido van Rossum <gu...@python.org> wrote: > - Most importantly: calling len(obj) and catching TypeError can only > be a substitute for the real implementation, which IMO ought to check > for the presence of a tp_len slot. Alas, checking hasattr(obj, > '__len__') doesn't quite cut it either, since this returns true for a > class object that defines a __len__ method for its instances (the > class itself doesn't have a length).
This isn't the only place this pattern comes up; maybe a hasmethod() function somewhere (builtin, operator, inspect?) for this would be a good idea. (i.e., something that returns true only if the method is for the instance.) (But perhaps that's a python-ideas topic, since it raises the question of whether it should really be something more like instancehasattr(), or whether it should be limited to special slots or something else.) _______________________________________________ Python-Dev mailing list Python-Dev@python.org http://mail.python.org/mailman/listinfo/python-dev Unsubscribe: http://mail.python.org/mailman/options/python-dev/archive%40mail-archive.com
