ModelDoesNotExist

ModelDoesNotExist is an exception class used in Django’s ORM to signal that a requested model instance cannot be found in the database. It acts as the base class for errors raised when a query does not return a matching object.

In normal operation, Django raises a model-specific subclass such as MyModel.DoesNotExist when a lookup via get() fails to locate a row. These model-specific exceptions inherit from ModelDoesNotExist, allowing developers to catch either the generic base or the specific subclass depending on the desired scope of error handling.

This mechanism helps differentiate missing objects from other types of database errors. Catching ModelDoesNotExist will handle missing instances for any model, while catching MyModel.DoesNotExist targets only that particular model. The approach is commonly used alongside Django’s get_object_or_404 helper, which converts a DoesNotExist exception into a 404 Not Found response in web applications.

ModelDoesNotExist is part of a broader exception hierarchy that includes ObjectDoesNotExist (and other DoesNotExist types) used by Django to signal missing data across different parts of the framework. While many missing-object scenarios are handled with the model-specific DoesNotExist subclass, the base ModelDoesNotExist provides a uniform entry point for generic error handling.

In summary, ModelDoesNotExist represents missing model instances in Django’s ORM. It underpins robust error handling for database lookups and is typically subclassed by each model’s own DoesNotExist exception to enable precise or broad-catching strategies.