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

[Chris Barker]

On Tue, Jul 3, 2018 at 12:01 PM, David Mertz <mertz at gnosis.cx> wrote:

> ... but I STILL like a new collections.Grouping (or collections.Grouper)
> the best.
>

me too.


> It might overcome Guido's reluctance... and what goes there is really
> delegated by him, not his own baby.
>

Is collections anyone in particular's baby? like itertools "belongs" to
Raymond?

-CHB




> On Tue, Jul 3, 2018 at 12:19 PM Chris Barker via Python-ideas <
> python-ideas at python.org> 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
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>
>
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-- 

Christopher Barker, Ph.D.
Oceanographer

Emergency Response Division
NOAA/NOS/OR&R            (206) 526-6959   voice
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Chris.Barker at noaa.gov
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