=================
Django Exceptions
=================


Django raises some Django specific exceptions as well as many standard
Python exceptions.

Django-specific Exceptions
==========================

.. module:: django.core.exceptions
    :synopsis: Django specific exceptions

ObjectDoesNotExist and DoesNotExist
-----------------------------------
.. exception:: DoesNotExist
.. exception:: ObjectDoesNotExist

    The :exc:`DoesNotExist` exception is raised when an object is not found
    for the given parameters of a query.

    :exc:`ObjectDoesNotExist` is defined in :mod:`django.core.exceptions`.
    :exc:`DoesNotExist` is a subclass of the base :exc:`ObjectDoesNotExist`
    exception that is provided on every model class as a way of
    identifying the specific type of object that could not be found.

    See :meth:`~django.db.models.QuerySet.get()` for further information
    on :exc:`ObjectDoesNotExist` and :exc:`DoesNotExist`.

MultipleObjectsReturned
-----------------------
.. exception:: MultipleObjectsReturned

    The :exc:`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 :mod:`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 :meth:`~django.db.models.QuerySet.get()` for further information.

SuspiciousOperation
-------------------
.. exception:: SuspiciousOperation

    The :exc:`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.

PermissionDenied
----------------
.. exception:: PermissionDenied

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

ViewDoesNotExist
----------------
.. exception:: ViewDoesNotExist

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

MiddlewareNotUsed
-----------------
.. exception:: MiddlewareNotUsed

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

ImproperlyConfigured
--------------------
.. exception:: ImproperlyConfigured

    The :exc:`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

    The :exc:`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

    The :exc:`ValidationError` exception is raised when data fails form or
    model field validation. For more information about validation, see
    :doc:`Form and Field Validation </ref/forms/validation>`,
    :ref:`Model Field Validation <validating-objects>` and the
    :doc:`Validator Reference </ref/validators>`.

Database Exceptions
===================

Django wraps the standard database exceptions :exc:`DatabaseError` and
:exc:`IntegrityError` so that your Django code has a guaranteed common
implementation of these classes. These database exceptions are
provided in :mod:`django.db`.

The Django wrappers for database exceptions behave exactly the same as
the underlying database exceptions. See `PEP 249 - Python Database API
Specification v2.0`_ for further information.

.. _`PEP 249 - Python Database API Specification v2.0`: http://www.python.org/dev/peps/pep-0249/

Python Exceptions
=================

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

.. _`documentation`: http://docs.python.org/lib/module-exceptions.html
