On Wed, Jul 21, 2010 at 12:04 PM, Darius Damalakas <
darius.damala...@gmail.com> wrote:
> Hi,
>
> I want to select a single object or get None if my query does not
> return a single object.
>
>
> So far here is what i have found in the docs (http://
> docs.djangoproject.com/en/dev/topics/db/queries/#limiting-querysets):
>
> ------------------------------------
> To retrieve a single object rather than a list (e.g. SELECT foo FROM
> bar LIMIT 1), use a simple index instead of a slice. For example,
> this returns the first Entry in the database, after ordering entries
> alphabetically by headline:
>
> >>> Entry.objects.order_by('headline')[0]
>
> This is roughly equivalent to:
>
> >>> Entry.objects.order_by('headline')[0:1].get()
>
> Note, however, that the first of these will raise IndexError while the
> second will raise DoesNotExist if no objects match the given criteria.
> See get() for more details.
> ------------------------------------
>
> Unfortunately, both ways generate an exception, which is bad.
>
> Is there some kind of way to either get a single object and evaluate
> the query, or get None instead?
> NHibernate and LINQ has a way to do that, so i wonder does Django have
> that
>
>
> Darius
try:
obj = Entry.objects.order_by('headline')[0:1].get()
except Entry.DoesNotExist:
obj = None
This is pretty standard. There has been some discussion on a get_or_none
style function on querysets, but I think we will have to wait a version for
it.
Also look up django.shortcuts.get_object_or_404
Hope that helps,
Michael
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