How do I get the object if it exists, or None if it does not exist?

Question

When I ask the model manager to get an object, it raises DoesNotExist when there is no matching object.

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


        

Answer 1

Handling exceptions at different points in your views could really be cumbersome..What about defining a custom Model Manager, in the models.py file, like

class ContentManager(model.Manager):
    def get_nicely(self, **kwargs):
        try:
            return self.get(kwargs)
        except(KeyError, Content.DoesNotExist):
            return None

and then including it in the content Model class

class Content(model.Model):
    ...
    objects = ContentManager()

In this way it can be easily dealt in the views i.e.

post = Content.objects.get_nicely(pk = 1)
if post:
    # Do something
else:
    # This post doesn't exist

Answer 2

It's one of those annoying functions that you might not want to re-implement:

from annoying.functions import get_object_or_None
#...
user = get_object_or_None(Content, name="baby")

Answer 3

you could use exists with a filter:

Content.objects.filter(name="baby").exists()
#returns False or True depending on if there is anything in the QS

just an alternative for if you only want to know if it exists

Answer 4

Maybe is better you use:

User.objects.filter(username=admin_username).exists()

Answer 5

From django 1.7 onwards you can do like:

class MyQuerySet(models.QuerySet):

    def get_or_none(self, **kwargs):
        try:
            return self.get(**kwargs)
        except self.model.DoesNotExist:
            return None


class MyBaseModel(models.Model):

    objects = MyQuerySet.as_manager()


class MyModel(MyBaseModel):
    ...

class AnotherMyModel(MyBaseModel):
    ...

The advantage of "MyQuerySet.as_manager()" is that both of the following will work:

MyModel.objects.filter(...).get_or_none()
MyModel.objects.get_or_none()

Answer 6

I was facing with the same problem too. It's hard to write and read try-except for each time when you want to get an element from your model as in @Arthur Debert's answer. So, my solution is to create an Getter class which is inherited by the models:

class Getter:
    @classmethod
    def try_to_get(cls, *args, **kwargs):
        try:
            return cls.objects.get(**kwargs)
        except Exception as e:
            return None

class MyActualModel(models.Model, Getter):
    pk_id = models.AutoField(primary_key=True)
    ...

In this way, I can get the actual element of MyActualModel or None:

MyActualModel.try_to_get(pk_id=1)