[Python-ideas] Possible new itertool: comm()

Antoine Pitrou solipsis at pitrou.net
Tue Jan 6 19:36:55 CET 2015


On Tue, 6 Jan 2015 18:22:44 +0000
Paul Moore <p.f.moore at gmail.com> wrote:
> On 6 January 2015 at 17:14, Raymond Hettinger
> <raymond.hettinger at gmail.com> wrote:
> >> On Jan 6, 2015, at 8:22 AM, Paul Moore <p.f.moore at gmail.com> wrote:
> >>
> >> In writing a utility script today, I found myself needing to do
> >> something similar to what the Unix "comm" utility does - take two
> >> sorted iterators, and partition the values into "only in the first",
> >> "only in the second", and "in both" groups.
> >
> > As far as I can tell, this would be a very rare need.
> 
> It's come up for me a few times, usually when trying to check two
> lists of files to see which ones have been missed by a program, and
> which ones the program thinks are present but no longer exist.

Why don't you use sets for such things? Your iterator is really only
useful for huge or unhashable inputs.

Regards

Antoine.




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