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In Django, how do I obtain the object if it exists, or None if it doesn’t?

Category: python

Tag: , ,

Problem

When I ask the model manager to get an object, it returns DoesNotExist since no such object exists.

go = Content.objects.get(name="baby")

Instead of DoesNotExist, how can I have go be None instead?

Asked by TIMEX

Solution #1

There isn’t a ‘built-in’ technique to accomplish this. Django will always throw the DoesNotExist exception. In Python, the customary approach to deal with this is to encapsulate it in a try catch:

try:
    go = SomeModel.objects.get(foo='bar')
except SomeModel.DoesNotExist:
    go = None

I did, however, subclass models. Create a safe get like the code above and use that manager for my models, manager. You can write: SomeModel.objects.safe get(foo=’bar’) in this way.

Answered by Arthur Debert

Solution #2

Since Django 1.6, you can utilize the first() function in the following way:

Content.objects.filter(name="baby").first()

Answered by FeroxTL

Solution #3

From django docs

You can catch the exception and assign None to go.

from django.core.exceptions import ObjectDoesNotExist
try:
    go  = Content.objects.get(name="baby")
except ObjectDoesNotExist:
    go = None

Answered by Amarghosh

Solution #4

This can be done with a generic function.

def get_or_none(classmodel, **kwargs):
    try:
        return classmodel.objects.get(**kwargs)
    except classmodel.DoesNotExist:
        return None

Use it as follows:

go = get_or_none(Content,name="baby")

going to be If no entry matches, nothing is returned; otherwise, the Content entry is returned.

Note:It will raises exception MultipleObjectsReturned if more than one entry returned for name=”baby”.

To avoid this type of issue, you should handle it on the data model, although you may want to log it at run time like this:

def get_or_none(classmodel, **kwargs):
    try:
        return classmodel.objects.get(**kwargs)
    except classmodel.MultipleObjectsReturned as e:
        print('ERR====>', e)

    except classmodel.DoesNotExist:
        return None

Answered by Ranju R

Solution #5

This is how you can go about it:

go  = Content.objects.filter(name="baby").first()

Now either the object you want or None can be used as the go variable.

Ref: https://docs.djangoproject.com/en/1.8/ref/models/querysets/#django.db.models.query.QuerySet.first

Answered by Gaurav

Post is based on https://stackoverflow.com/questions/3090302/how-do-i-get-the-object-if-it-exists-or-none-if-it-does-not-exist-in-django