[Python-ideas] Unpacking a dict

[Nikolaus Rath]

On May 31 2016, Paul Moore <p.f.moore-Re5JQEeQqe8AvxtiuMwx3w at public.gmane.org> wrote:
> On 31 May 2016 at 20:57, Nikolaus Rath <Nikolaus-BTH8mxji4b0 at public.gmane.org> wrote:
>> On May 31 2016, Paul Moore <p.f.moore-Re5JQEeQqe8AvxtiuMwx3w-XMD5yJDbdMReXY1tMh2IBg at public.gmane.org> wrote:
>>> Technically, the "export key" approach could probably me made readable
>>> in a way I'd be OK with, for example:
>>>
>>> export key from query_result (
>>>     product_id,
>>>     quantity,
>>>     distributor,
>>>     description
>>> )
>>>
>>> but I'm not at all sure that needing 2 new keywords ("export" and
>>> "key") and a reuse of an existing one ("from") is going to fly - it's
>>> too wordy, feels like SQL or COBOL to me. Maybe if someone comes up
>>> with a one-word option for "export key from" then it would be
>>> viable...
>>
>> How about
>>
>>   unravel query_result (this, that, something)
>
> Meh. Don't assume that if you come up with a good word, I'll be in
> favour. At best, I'll go from -1 to -0 or maybe +0. Should we get to
> something that looks reasonably attractive to me, there's still issues
> with the whole thing being a niche problem, limited applicability (by
> leaping at "unravel" you lost the ability to extract attributes from
> an object - did you mean to do that?), etc.
>
> Basically, don't waste too much time trying to convince me. A better
> bet would be to get sufficient support from others that my opinion is
> irrelevant (which it may well be anyway :-))

Nah, I think I don't like my own idea anymore. I think the whole issue
is much better addressed by using an assignment with a placeholder on
the LHS. This also solves the DRY problem when creating things like
namedtuples:

d = query_result
product_id = q[$lhs]
quantity = q[$lhs]
distributor = q[$lhs]
description = q[$lhs]

# or

my_favorite_named_tuple = namedtuple($lhs, "foo bar com")


$lhs would be a special construct that is only allowed in the RHS of an
assignment statement and evaluates to a string representation of the
identifier on the LHS.


But since I don't have time to learn how to extend the Python parser, I
will shut up about this now.


Best,
-Nikolaus

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