[George Sakkis] > The fact that strings don't have __iter__ is an implementation > detail. I can't think of any reason other than historic and perhaps > backwards compatibility for this; > iterables should IMHO by definition be exactly > the objects with __iter__).
There would be no benefit other than satisfying that particular world view. It is a feature that all sequences are automatically iterable without having to write a custom __iter__ method. That makes life a bit easier for writers of sequence-like classes. [Michele Simionato] > I think strings do not have __iter__ on purpose, exactly to > distinguish them from other iterables, since sometimes it is nice > to consider them atomic, but I am not sure of this. You should > ask the developers. That is not correct. Since any sequence is automatically iterable (because of the presence of __getitem__), the inclusion of a separate __iter__ method is purely optional. The option to include a custom __iter__ method has been exercised only when it has offered some performance benefit. IOW, the inclusion of __iter__ for a sequence is an arbitrary implementation detail -- there is no other significance. > Anyway, the right definition of iterable is > (as I was told) "an object X such that iter(X) does not throw an > exception". Objects following the __getitem__ protocol >- such as strings -are iterables even if they do not have >an __iter__ method. An object is iterable if and only if it provides either __iter__ or __getitem__. Raymond -- http://mail.python.org/mailman/listinfo/python-list
