[Python-ideas] Enhancing dict.values

[Koos Zevenhoven]

On Fri, May 27, 2016 at 7:57 AM, Ethan Furman <ethan at stoneleaf.us> wrote:

> On 05/26/2016 09:26 PM, Guido van Rossum wrote:
>
>> On Thursday, May 26, 2016, Steven D'Apranowrote:
>>
>>> On Thu, May 26, 2016 at 11:28:25PM +0100, Nathan Schneider wrote:
>>>
>>
> I think this is important enough to get a change in subject line, lest
>>> it be lost in the dict unpacking thread.
>>>
>>
>>
>>
>> Instead of special syntax, what if dict.values() returned a tuple
>>>>
>>> when given keys as arguments:
>>>
>>>>
>>>>    partner_id, product_id, ship_to, product_ids = my_dict.values(
>>>>            'partner_id', 'product_id', 'ship_to', 'product_ids')
>>>>
>>>> That avoids repeating the dict variable, at least. And as there is
>>>> dict.update(), I don't see the need for a new syntax for assigning to
>>>> multiple keys.
>>>>
>>>
>>> I like this idea. I think it beats the status quo:
>>>
>>> +1
>>>
>>
>> Interesting. It should probably have a different name. What type should
>> it return? Iterator? Sequence? It can't really be a ValuesView because
>> that class is just a view on the hash table. Even though you technically
>> *could* combine this functionality into values(), I don't think it would
>> be helpful to do so -- if only because of the surprising edge case where
>> if you were to pass it a list of keys to extract using **args, if the
>> list is empty, values() would default to its original behavior or
>> returning all keys, in hash table order.
>>
>
> Good point.  The time bomb would be even worse if sometimes the dict had
> the same number of elements as were being asked for, as then it would be an
> intermittent problem.
>
> However, if we make a new method we could just as easily make a new
> function:
>
>   def get_values_from(a_dict, keys=()):
>       if not keys:
>            raise an_error
>       yield a_dict[k] for k in keys
>
> Hmmm.  That could even be handy for a list/tuple:
>
>   offset, name = get_values_from(a_list, [1, 7])
>
> ;)
>
>
​getitems(obj, subscripts) ?

We almost have this:

from operator import itemgetter

itemgetter(1,7)(a_list)

​-- Koos​



> At any rate, the return type should be an iterator.
>
> --
> ~Ethan~
>
>
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