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django/docs/ref/exceptions.txt
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=================
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
-----------------------------------
The ``DoesNotExist`` exception is raised when an object is not found
for the given parameters of a query.
``ObjectDoesNotExist`` is defined in ``django.core.exceptions``.
``DoesNotExist`` is a subclass of the base ``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 ``ObjectDoesNotExist`` and ``DoesNotExist``.
MultipleObjectsReturned
-----------------------
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 :meth:`~django.db.models.QuerySet.get()` for further information.
SuspiciousOperation
-------------------
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.
PermissionDenied
----------------
The ``PermissionDenied`` exception is raised when a user does not have
permission to perform the action requested.
ViewDoesNotExist
----------------
The ``ViewDoesNotExist`` exception is raised by
``django.core.urlresolvers`` when a requested view does not exist.
MiddlewareNotUsed
-----------------
The ``MiddlewareNotUsed`` exception is raised when a middleware is not
used in the server configuration.
ImproperlyConfigured
--------------------
The ``ImproperlyConfigured`` exception is raised when Django is
somehow improperly configured -- for example, if a value in ``settings.py``
is incorrect or unparseable.
FieldError
----------
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
- If a field cannot be determined from a keyword in the query
parameters
- If a join is not permitted on the specified field
- If a field name is invalid
- If a query contains invalid order_by arguments
Database Exceptions
===================
Django wraps the standard database exceptions ``DatabaseError`` and
``IntegrityError`` so that your Django code has a guaranteed common
implementation of these classes. These database exceptions are
provided in ``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