Django raises some of its own exceptions as well as standard Python exceptions.
Django Core Exceptions¶
Django core exception classes are defined in
This exception is raised when attempting to use models before the app loading process, which initializes the ORM, is complete.
The base class for
DoesNotExistexceptions for all models.
get()for further information on
EmptyResultSetmay be raised during query generation if a query won’t return any results. Most Django projects won’t encounter this exception, but it might be useful for implementing custom lookups and expressions.Changed in Django 1.11:
In older versions, it’s only importable from
MultipleObjectsReturnedexception is raised by a query if only one object is expected, but multiple objects are returned. A base version of this exception is provided in
django.core.exceptions; each model class contains a subclassed version that can be used to identify the specific object type that has returned multiple objects.
get()for further information.
SuspiciousOperationexception is raised when a user has performed an operation that should be considered suspicious from a security perspective, such as tampering with a session cookie. Subclasses of
SuspiciousOperationexception reaches the WSGI handler level it is logged at the
Errorlevel and results in a
HttpResponseBadRequest. See the logging documentation for more information.
PermissionDeniedexception is raised when a user does not have permission to perform the action requested.
ViewDoesNotExistexception is raised by
django.urlswhen a requested view does not exist.
MiddlewareNotUsedexception is raised when a middleware is not used in the server configuration.
ImproperlyConfiguredexception is raised when Django is somehow improperly configured – for example, if a value in
settings.pyis incorrect or unparseable.
FieldErrorexception is raised when there is a problem with a model field. This can happen for several reasons:
- A field in a model clashes with a field of the same name from an abstract base class
- An infinite loop is caused by ordering
- A keyword cannot be parsed from the filter parameters
- A field cannot be determined from a keyword in the query parameters
- A join is not permitted on the specified field
- A field name is invalid
- A query contains invalid order_by arguments
ValidationErrorexception is raised when data fails form or model field validation. For more information about validation, see Form and Field Validation, Model Field Validation and the Validator Reference.
URL Resolver exceptions¶
URL Resolver exceptions are defined in
Deprecated since version 1.10: In older versions, these exceptions are located in
django.core.urlresolvers. Importing from the old location will continue
to work until Django 2.0.
Resolver404exception is raised by
resolve()if the path passed to
resolve()doesn’t map to a view. It’s a subclass of
NoReverseMatchexception is raised by
django.urlswhen a matching URL in your URLconf cannot be identified based on the parameters supplied.
Database exceptions may be imported from
Django wraps the standard database exceptions so that your Django code has a guaranteed common implementation of these classes.
The Django wrappers for database exceptions behave exactly the same as the underlying database exceptions. See PEP 249, the Python Database API Specification v2.0, for further information.
As per PEP 3134, a
__cause__ attribute is set with the original
(underlying) database exception, allowing access to any additional
information provided. (Note that this attribute is available under
both Python 2 and Python 3, although PEP 3134 normally only applies
to Python 3. To avoid unexpected differences with Python 3, Django will also
ensure that the exception made available via
__cause__ has a usable
__traceback__ attribute described above was added.
Raised to prevent deletion of referenced objects when using
models.ProtectedError is a subclass
Http exceptions may be imported from
UnreadablePostErroris raised when a user cancels an upload.
Transaction exceptions are defined in
TransactionManagementErroris raised for any and all problems related to database transactions.
Testing Framework Exceptions¶
Exceptions provided by the
RedirectCycleErroris raised when the test client detects a loop or an overly long chain of redirects.
Django raises built-in Python exceptions when appropriate as well. See the Python documentation for further information on the Built-in Exceptions.