On Thu, Jun 28, 2018 at 10:24 AM Rob Cliffe via Python-ideas <
python-ideas@python.org> wrote:
> def group_by(iterable, groupfunc, itemfunc=lambda x:x, sortfunc=lambda
> x:x): # Python 2 & 3 compatible!
>
> D = {}
> for x in iterable:
> group = groupfunc(x)
> D[group] = D.get(group, []) + [itemfunc(x)]
> if sortfunc is not None:
> for group in D:
> D[group] = sorted(D[group], key=sortfunc)
> return D
>
The fact that you didn't use ``setdefault`` here, opting for repeatedly
constructing new lists via concatenation, demonstrates the need for a
built-in or standard library tool that is easier to use.
I'll submit a proposal for your review soon.
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