I wrote: > # I want to do ``dd[item] += 1`` Guido van Rossum wrote: > You don't need a new feature for that use case; d[k] = d.get(k, 0) + 1 > is perfectly fine there and hard to improve upon.
Alex Martelli wrote: > I see d[k]+=1 as a substantial improvement -- conceptually more > direct, "I've now seen one more k than I had seen before". Guido van Rossum wrote: > Yes, I now agree. This means that I'm withdrawing proposal A (new > method) and championing only B (a subclass that implements > __getitem__() calling on_missing() and on_missing() defined in that > subclass as before, calling default_factory unless it's None). Probably already obvious from my previous post, but FWIW, +1. Two unaddressed issues: * What module should hold the type? I hope the collections module isn't too controversial. * Should default_factory be an argument to the constructor? The three answers I see: - "No." I'm not a big fan of this answer. Since the whole point of creating a defaultdict type is to provide a default, requiring two statements (the constructor call and the default_factory assignment) to initialize such a dictionary seems a little inconvenient. - "Yes and it should be followed by all the normal dict constructor arguments." This is okay, but a few errors, like ``defaultdict({1:2})`` will pass silently (until you try to use the dict, of course). - "Yes and it should be the only constructor argument." This is my favorite mainly because I think it's simple, and I couldn't think of good examples where I really wanted to do ``defaultdict(list, some_dict_or_iterable)`` or ``defaultdict(list, **some_keyword_args)``. It's also forward compatible if we need to add some of the dict constructor args in later. STeVe -- Grammar am for people who can't think for myself. --- Bucky Katt, Get Fuzzy _______________________________________________ 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