Django Exceptions

An exception is an abnormal event that leads to program failure. To deal with this situation, Django uses its own exception classes and supports all core Python exceptions as well.

Django core exceptions classes are defined in django.core.exceptions module. This module contains the following classes.

Django Exception Classes

Exception	Description
AppRegistryNotReady	It is raised when attempting to use models before the app loading process.
ObjectDoesNotExist	The base class for DoesNotExist exceptions.
EmptyResultSet	If a query does not return any result, this exception is raised.
FieldDoesNotExist	It raises when the requested field does not exist.
MultipleObjectsReturned	This exception is raised by a query if only one object is expected, but multiple objects are returned.
SuspiciousOperation	This exception is raised when a user has performed an operation that should be considered suspicious from a security perspective.
PermissionDenied	It is raised when a user does not have permission to perform the action requested.
ViewDoesNotExist	It is raised by django.urls when a requested view does not exist.
MiddlewareNotUsed	It is raised when a middleware is not used in the server configuration.
ImproperlyConfigured	The ImproperlyConfigured exception is raised when Django is somehow improperly configured.
FieldError	It is raised when there is a problem with a model field.
ValidationError	It is raised when data validation fails form or model field validation.

Django URL Resolver Exceptions

These exceptions are defined in django.urls module.

Exception	Description
Resolver404	This exception raised when the path passed to resolve() function does not map to a view.
NoReverseMatch	It is raised when a matching URL in your URLconf cannot be identified based on the parameters supplied.

Django Database Exceptions

The following exceptions are defined in django.db module.

Exception	Description
DatabaseError	It occurs when the database is not available.
IntegrityError	It occurs when an insertion query executes.
DataError	It raises when data related issues come into the database.

Django Http Exceptions

The following exceptions are defined in django.http module.

Exception	Description
UnreadablePostError	It is raised when a user cancels an upload.

Django Transaction Exceptions

The transaction exceptions are defined in django.db.transaction.

Exception	Description
TransactionManagementError	It is raised for any and all problems related to database transactions.

Django Exception Example

Suppose, we want to get employee record where id = 12, our view function will look below. It raises a DoesNotExist exception if data not found. This is Django’s built-in exception.

// views.py

def getdata(request):  

    data = Employee.objects.get(id=12)  

    return HttpResponse(data)

// urls.py

path('get',views.getdata)

It shows the following exception because no record is available at id 12.

Output:

We can handle it by using try and except, now let’s handle this exception.

// Views.py

def getdata(request):  

    try:  

        data = Employee.objects.get(id=12)  

    except ObjectDoesNotExist:  

        return HttpResponse("Exception: Data not found")  

    return HttpResponse(data);