Hi,
This is exactly what i do not want - to manually catch exceptions.
get_or_none function is what i need, but sad it's not here yet.
I hope when i will get to know python better, i will learn how to add
methods to all instances of some class, then i could add this method
myself. I know with javascript prototyping inheritance that is easily
possible. Not sure about python though
Thanks for the answer. That is sufficient
On 21 July, 19:23, Michael <newmani...@gmail.com> wrote:
> 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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