[Python-ideas] Where should grouping() live (was: grouping / dict of lists)

[Chris Barker]

It seems a really stupid reason to make this choice, but:

If we make a Grouping class, it has an obvious home in the collections
module

If we make a grouping (or grouped) function, we don't know where to put it

But since I like the Grouping class idea anyway, it's one more reason...

-CHB


On Tue, Jul 3, 2018 at 9:15 AM, Chris Barker <chris.barker at noaa.gov> wrote:

> On Tue, Jul 3, 2018 at 8:24 AM, Steven D'Aprano <steve at pearwood.info>
> wrote:
>
>> On Tue, Jul 03, 2018 at 09:23:07AM -0400, David Mertz wrote:
>>
>
>
>> > My problem with the second idea is that *I* find it very wrong to have
>> > something in itertools that does not return an iterator.  It wrecks the
>> > combinatorial algebra of the module.
>>
>
> hmm -- that seems to be a pretty pedantic approach -- practicality beats
> purity, after all :-)
>
> I think we should first decide if a grouping() function is a useful
> addition to the standard library (after all:  "not every two line function
> needs to in the stdlib"), and f so, then we can find a home for it.
>
> personally, I'm wondering if a "dicttools" or something module would make
> sense -- I imagine there are all sorts of other handy utilities for working
> with dicts that could go there. (though, yeah, we'd want to actually have a
> handful of these before creating a new module :-) )
>
> > That said, it's easy to fix... and I believe independently useful.  Just
>> > make grouping() a generator function rather than a plain function.  This
>> > lets us get an incremental grouping of an iterable.
>>
>> We already have something which lazily groups an iterable, returning
>> groups as they are seen: groupby.
>>
>> What makes grouping() different from groupby() is that it accumulates
>> ALL of the subgroups rather than just consecutive subgroupings.
>
>
> well, yeah, but it wont actually get you those until you exhaust the
> iterator -- so while it's different than itertools.groupby, it is different
> than itertools.groupby(sorted(iterable))?
>
> In short, this wouldn't really solve the problems that itertools.groupby
> has for this sort of task -- so what's the point?
>
>  > As for where it belongs, perhaps the collections module is the least
> worst fit.
>
> That depends some on whether we go with a simple function, in which case
> collections is a pretty bad fit (but maybe still the least worse).
>
> Personally I still like the idea of having this be special type of dict,
> rather than "just a function" -- and then it's really obvious where to put
> it :-)
>
> -CHB
>
>
> --
>
> Christopher Barker, Ph.D.
> Oceanographer
>
> Emergency Response Division
> NOAA/NOS/OR&R            (206) 526-6959   voice
> 7600 Sand Point Way NE   (206) 526-6329   fax
> Seattle, WA  98115       (206) 526-6317   main reception
>
> Chris.Barker at noaa.gov
>



-- 

Christopher Barker, Ph.D.
Oceanographer

Emergency Response Division
NOAA/NOS/OR&R            (206) 526-6959   voice
7600 Sand Point Way NE   (206) 526-6329   fax
Seattle, WA  98115       (206) 526-6317   main reception

Chris.Barker at noaa.gov
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