Django Exceptions

Django raises some of its own exceptions as well as standard Python exceptions.

Django Core Exceptions

Django core exception classes are defined in django.core.exceptions.

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.

exception ObjectDoesNotExist[source]

The base class for DoesNotExist exceptions; a try/except for ObjectDoesNotExist will catch DoesNotExist exceptions for all models.

See get() for further information on ObjectDoesNotExist and DoesNotExist.

FieldDoesNotExist

exception FieldDoesNotExist[source]

The FieldDoesNotExist exception is raised by a model’s _meta.get_field() method when the requested field does not exist on the model or on the model’s parents.

Changed in Django 1.8:

This exception was previously defined only in django.db.models.fields and wasn’t part of the public API.

MultipleObjectsReturned

exception MultipleObjectsReturned[source]

The MultipleObjectsReturned exception 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.

See get() for further information.

SuspiciousOperation

exception SuspiciousOperation[source]

The SuspiciousOperation exception 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 SuspiciousOperation include:

  • DisallowedHost
  • DisallowedModelAdminLookup
  • DisallowedModelAdminToField
  • DisallowedRedirect
  • InvalidSessionKey
  • SuspiciousFileOperation
  • SuspiciousMultipartForm
  • SuspiciousSession

If a SuspiciousOperation exception reaches the WSGI handler level it is logged at the Error level and results in a HttpResponseBadRequest. See the logging documentation for more information.

PermissionDenied

exception PermissionDenied[source]

The PermissionDenied exception is raised when a user does not have permission to perform the action requested.

ViewDoesNotExist

exception ViewDoesNotExist[source]

The ViewDoesNotExist exception is raised by django.core.urlresolvers when a requested view does not exist.

MiddlewareNotUsed

exception MiddlewareNotUsed[source]

The MiddlewareNotUsed exception is raised when a middleware is not used in the server configuration.

ImproperlyConfigured

exception ImproperlyConfigured[source]

The ImproperlyConfigured exception is raised when Django is somehow improperly configured – for example, if a value in settings.py is incorrect or unparseable.

FieldError

exception FieldError[source]

The FieldError exception 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

ValidationError

exception ValidationError[source]

The ValidationError exception 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.

NON_FIELD_ERRORS

NON_FIELD_ERRORS

ValidationErrors that don’t belong to a particular field in a form or model are classified as NON_FIELD_ERRORS. This constant is used as a key in dictionaries that otherwise map fields to their respective list of errors.

URL Resolver exceptions

URL Resolver exceptions are defined in django.core.urlresolvers.

Resolver404

exception Resolver404[source]

The Resolver404 exception is raised by django.core.urlresolvers.resolve() if the path passed to resolve() doesn’t map to a view. It’s a subclass of django.http.Http404.

NoReverseMatch

exception NoReverseMatch[source]

The NoReverseMatch exception is raised by django.core.urlresolvers when a matching URL in your URLconf cannot be identified based on the parameters supplied.

Database Exceptions

Database exceptions may be imported from django.db.

Django wraps the standard database exceptions so that your Django code has a guaranteed common implementation of these classes.

exception Error
exception InterfaceError
exception DatabaseError
exception DataError
exception OperationalError
exception IntegrityError
exception InternalError
exception ProgrammingError
exception NotSupportedError

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.)

exception models.ProtectedError

Raised to prevent deletion of referenced objects when using django.db.models.PROTECT. models.ProtectedError is a subclass of IntegrityError.

Http Exceptions

Http exceptions may be imported from django.http.

UnreadablePostError

exception UnreadablePostError

UnreadablePostError is raised when a user cancels an upload.

Transaction Exceptions

Transaction exceptions are defined in django.db.transaction.

TransactionManagementError

exception TransactionManagementError[source]

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

Testing Framework Exceptions

Exceptions provided by the django.test package.

RedirectCycleError

exception client.RedirectCycleError
New in Django 1.8.

RedirectCycleError is raised when the test client detects a loop or an overly long chain of redirects.

Python Exceptions

Django raises built-in Python exceptions when appropriate as well. See the Python documentation for further information on the Built-in Exceptions.

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