[Python-Dev] Re: Should set objects maintain insertion order too?

2019年12月20日 06:11:22 -0800

Got it. Thanks
On Fri, Dec 20, 2019, 2:34 AM Inada Naoki <[email protected]> wrote:
> On Fri, Dec 20, 2019 at 4:15 PM Wes Turner <[email protected]> wrote:
> >
> > How slow and space-inefficient would it be to just implement the set
> methods on top of dict?
>
> Speed: Dict doesn't cache the position of the first item. Calling
> next(iter(D)) repeatedly is O(N) in worst case.
> Space: It waste 8bytes per member.
>
> >
> > Do dicts lose insertion order when a key is deleted? AFAIU, OrderedDict
> do not lose insertion order on delete.
>
> Dict keeps insertion order after deletion too.
>
> >Would this limit the utility of an ordered set as a queue? What set
> methods does a queue need to have?
>
> I want O(1) D.popleft(). (The name is borrowed from deque. popfirst()
> would be better maybe).
>
> --
> Inada Naoki <[email protected]>
>
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