Where do I import the `DoesNotExist` exception in Django 1.10 from?

Question

I'm having trouble figuring this out. I'm trying to catch an exception in the case of a specific object not existing, but the line

from django.core.exceptions import DoesNotExist

gives me the cannot find reference in exeptions.py warning. If the exception is not specified in that file, where do I find it?

Answer 1

The exception is called ObjectDoesNotExists [Django-doc] in case the model is not known, so you import it as:

from django.core.exceptions import ObjectDoesNotExist

The Object is used to avoid confusion with the DoesNotExist exception every model has (you can see Object as a "generalization" of objects of all models).

Note however that if you know what the model is of the model that you query for, it is better to use a more restricted exception, like:

try:
    SomeModel.objects.get(pk=14)
except SomeModel.DoesNotExist:
    # ... do something
    pass

Like specified in the documentation of the model attributes [Django-doc]:

Django provides a DoesNotExist exception as an attribute of each model class to identify the class of object that could not be found and to allow you to catch a particular model class with try/except. The exception is a subclass of django.core.exceptions.ObjectDoesNotExist.

Such that you do not - by accident - catch exceptions because some (related) model can not be fetched. Typically the span of a try-except block should be as small as possible, and the exception as "explicit" as possible.