How do you catch this exception?

Question

This code is in django/db/models/fields.py It creates/defines an exception?

class ReverseSingleRelatedObjectDescriptor(six.with_metaclass(RenameRelatedObjec         


        

Answer 1

If your related model is called Foo you can just do:

except Foo.DoesNotExist:

Django is amazing when its not terrifying. RelatedObjectDoesNotExist is a property that returns a type that is figured out dynamically at runtime. That type uses self.field.rel.to.DoesNotExist as a base class. According to Django documentation:

ObjectDoesNotExist and DoesNotExist

exception DoesNotExist

The DoesNotExist exception is raised when an object is not found for the given parameters of a query. 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.

This is the magic that makes that happen. Once the model has been built up, self.field.rel.to.DoesNotExist is the does-not-exist exception for that model.