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

The RelatedObjectDoesNotExist exception is created dynamically at runtime. Here is the relevant code snippet for the ForwardManyToOneDescriptor and ReverseOneToOneDescriptor descriptors:

@cached_property
def RelatedObjectDoesNotExist(self):
    # The exception can't be created at initialization time since the
    # related model might not be resolved yet; `self.field.model` might
    # still be a string model reference.
    return type(
        'RelatedObjectDoesNotExist',
        (self.field.remote_field.model.DoesNotExist, AttributeError),
        {}
    )

So the exception inherits from .DoesNotExist and AttributeError. In fact, the complete MRO for this exception type is:

[, 
.DoesNotExist'>,
,
,
,
,
]

The basic takeaway is you can catch .DoesNotExist, ObjectDoesNotExist (import from django.core.exceptions) or AttributeError, whatever makes the most sense in your context.