[Python-Dev] Re: Sets: elt in dict, lst.include
Mon, 29 Jan 2001 21:19:12 -0500
> I just wanted to hint at a problem which iterating over items
> in an unordered set can cause. Especially new Python users will find
> it confusing that the order of the items in an iteration can change
> from one run to the next.
Do they find "for k, v in dict.items()" confusing now? Would be the same.
> What we really want is iterators for dictionaries, so why not
> implement these instead of tweaking for-loops.
Seems an unrelated topic: would "iterators for dictionaries" solve the
supposed problem with iteration order?
> If you are looking for speedups w/r to for-loops, applying a
> different indexing technique in for-loops would go a lot further
> and provide better performance not only to dictionary loops,
> but also to other sequences.
> I have made some good experience with a special counter object
> (sort of like a mutable integer) which is used instead of the
> iteration index integer in the current implementation.
Please quantify, if possible. My belief (based on past experiments) is that
in loops fancier than
for i in range(n):
the loop overhead quickly falls into the noise even now.
> Using an iterator object instead of the integer + __getitem__
> call machinery would allow more flexibility for all kinds of
> sequences or containers. ...
This is yet another abrupt change of topic, yes <0.9 wink>? I agree a new
iteration *protocol* could have major attractions.