Document how to retrieve a single value using values_list() and get()

[Omer Katz]

This saves me the pain of typing the following code:
foo_pk = MyModel.objects.only('pk').get(name='foo').pk
Now you can type:
foo_pk = MyModel.objects.get_value('pk', name='foo')
Which is more intuitive.

Pull Request at ​https://github.com/django/django/pull/5004

[Florian Apolloner]

I think this could live on a custom queryset just fine (or even as free method), I cannot remember when I'd ever would have needed something like this. I know we have a few of "syntax sugar" methods like first and last, but those are used really often in code and having that as nice oneliners makes sense.

[Tim Graham]

I'm not particularly enthusiastic either, but it's better to first propose new APIs like this on the DevelopersMailingList so that the discussion involves a wider audience. I did notice that this patterns appears about 25 times in the test suite (grep -rI "only(" * | grep "get(" | wc -l), sometimes only() involves multiple fields though.

[Simon Charette]

FWIW this is already achievable with values_list('pk', flat=True).get(name='foo').

While we can argue the latter is a bit verbose I don't think the use case is common enough to warrant an addition to the QuerySet API.

[Omer Katz]

It is worth a documentation change at the very least.

[Omer Katz]

Also I added a bit of coverage for get(). Should I open a separate PR with those tests alone?

[Tim Graham]

I would think get() is pretty well tested by now. tests/basic seems to cover the simple stuff and the ​coverage report doesn't report any untested lines. Of course, if you think you have something new to offer, we'll take a look.

[Omer Katz]

I missed those. The tests are not very well organized for those who are unfamiliar with their structure. I guess I should try to contribute more :)
I'm not worry about the time I spent about this method as I learned something new about Django and because something might come out of it anyway,

I think we can close this issue and file a new one about documenting what charettes suggested because it's not something that is either widely known or intuitive. I expected to get a list/tuple even with flat=True.

[Omer Katz]

Sorry about that. Race condition :P

[Omer Katz]

Where do you guys think that this fits? In the queryset guide?

[Tim Graham]

Probably either in ref/models/querysets.txt under values_list or somewhere in topics/db/queries.txt.

[Alex Morozov]

PR is on it`s way.

[Alex Morozov]

​https://github.com/django/django/pull/5534

[Tim Graham <timograham@…>]

In 4373eac:

Fixed #25132 -- Documented how to retrieve a single value using values_list() and get().

[Tim Graham <timograham@…>]

In ecb3e314:

[1.9.x] Fixed #25132 -- Documented how to retrieve a single value using values_list() and get().

Backport of 4373eac99828d99718a7b245d160e7e64fce2e95 from master

[Tim Graham <timograham@…>]

In 676636ac:

[1.8.x] Fixed #25132 -- Documented how to retrieve a single value using values_list() and get().

Backport of 4373eac99828d99718a7b245d160e7e64fce2e95 from master