[Python-ideas] Allow a group by operation for dict comprehension

[David Mertz]

I think you cheated a little in your cut-and-paste.  `student_by_school` is
not defined in the code you've shown.  What you **did** define, `
student_school_list` doesn't give you what you want if you use `
defaultdict(list,student_school_list)`.

I thought for a moment I might just use:

[(b,a) for a,b in student_school_list]


But that's wrong for reasons that are probably obvious to everyone else.
I'm not really sure what `student_by_school` could possibly be to make this
work as shown.

On Thu, Jun 28, 2018 at 8:13 PM Chris Barker via Python-ideas <
python-ideas at python.org> wrote:

> In [97]: student_school_list
> Out[97]:
> [('Fred', 'SchoolA'),
>  ('Bob', 'SchoolB'),
>  ('Mary', 'SchoolA'),
>  ('Jane', 'SchoolB'),
>  ('Nancy', 'SchoolC')]
>
> In [98]: result = defaultdict(list, student_by_school)
>
> In [99]: result.items()
> Out[99]: dict_items([('SchoolA', ['Fred', 'Mary']), ('SchoolB', ['Bob',
> 'Jane']), ('SchoolC', ['Nancy'])])
>
> So: <small voice> never mind </small voice>
>
> -CHB
>
> --
>
> Christopher Barker, Ph.D.
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