Re: set and dict iteration

Newsgroups	comp.lang.python
Date	2012-09-03 13:04 -0700
References	(9 earlier) <mailman.3480.1345343315.4697.python-list@python.org> <c7452db1-5b78-4d54-81a1-1c8683631d6e@googlegroups.com> <mailman.3883.1346095064.4697.python-list@python.org> <1567e8c7-a2bb-41f4-9be8-18e9f4d063cb@googlegroups.com> <mailman.154.1346700607.27098.python-list@python.org>
Subject	Re: set and dict iteration
From	Aaron Brady <castironpi@gmail.com>
Message-ID	<mailman.155.1346702665.27098.python-list@python.org> (permalink)

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On Monday, September 3, 2012 2:30:24 PM UTC-5, Ian wrote:
> On Sun, Sep 2, 2012 at 11:43 AM, Aaron Brady <castironpi@gmail.com> wrote:
> 
> > We could use a Python long object for the version index to prevent overflow.  Combined with P. Rubin's idea to count the number of open iterators, most use cases still wouldn't exceed a single word comparison; we could reset the counter when there weren't any.
> 
> 
> 
> We could use a Python long; I just don't think the extra overhead is
> 
> justified in a data structure that is already highly optimized for
> 
> speed.  Incrementing and testing a C int is *much* faster than doing
> 
> the same with a Python long.

I think the technique would require two python longs and a bool in the set, and a python long in the iterator.

One long counts the number of existing (open) iterators.  Another counts the version.  The bool keeps track of whether an iterator has been created since the last modification, in which case the next modification requires incrementing the version and resetting the flag.

Thread

Re: set and dict iteration Ian Kelly <ian.g.kelly@gmail.com> - 2012-08-27 13:17 -0600
  Re: set and dict iteration Aaron Brady <castironpi@gmail.com> - 2012-09-02 10:43 -0700
    Re: set and dict iteration Ian Kelly <ian.g.kelly@gmail.com> - 2012-09-03 13:29 -0600
      Re: set and dict iteration Aaron Brady <castironpi@gmail.com> - 2012-09-03 13:04 -0700
        Re: set and dict iteration Dave Angel <d@davea.name> - 2012-09-03 16:27 -0400
          Re: set and dict iteration Aaron Brady <castironpi@gmail.com> - 2012-09-03 17:24 -0700
          Re: set and dict iteration Aaron Brady <castironpi@gmail.com> - 2012-09-03 17:24 -0700
      Re: set and dict iteration Aaron Brady <castironpi@gmail.com> - 2012-09-03 13:04 -0700
        Re: set and dict iteration Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2012-09-04 01:26 +0000
          Re: set and dict iteration Dave Angel <d@davea.name> - 2012-09-03 21:50 -0400
            Re: set and dict iteration Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2012-09-04 01:59 +0000
              Re: set and dict iteration Aaron Brady <castironpi@gmail.com> - 2012-09-08 08:42 -0700
  Re: set and dict iteration Aaron Brady <castironpi@gmail.com> - 2012-09-02 10:43 -0700

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