Viewing github.com/django/django-stable-4.1.x/docs/ref/exceptions.txt

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

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Django Core Exceptions
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======================
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```
.. module:: django.core.exceptions
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```
    :synopsis: Django core exceptions
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Django core exception classes are defined in ``django.core.exceptions``.

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``AppRegistryNotReady``
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-----------------------
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```
.. exception:: AppRegistryNotReady
```

    This exception is raised when attempting to use models before the :ref:`app

    loading process <app-loading-process>`, which initializes the ORM, is

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    complete.
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``ObjectDoesNotExist``
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----------------------
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.. exception:: ObjectDoesNotExist
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    The base class for :exc:`Model.DoesNotExist

    <django.db.models.Model.DoesNotExist>` exceptions. A ``try/except`` for

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    ``ObjectDoesNotExist`` will catch
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    :exc:`~django.db.models.Model.DoesNotExist` exceptions for all models.

    See :meth:`~django.db.models.query.QuerySet.get()`.

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``EmptyResultSet``
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------------------
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.. exception:: EmptyResultSet
```

    ``EmptyResultSet`` may 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.

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``FieldDoesNotExist``
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---------------------
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.. exception:: FieldDoesNotExist
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    The ``FieldDoesNotExist`` exception is raised by a model's

    ``_meta.get_field()`` method when the requested field does not exist on the

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    model or on the model's parents.
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``MultipleObjectsReturned``
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---------------------------
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.. exception:: MultipleObjectsReturned
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    The base class for :exc:`Model.MultipleObjectsReturned

    <django.db.models.Model.MultipleObjectsReturned>` exceptions. A

    ``try/except`` for ``MultipleObjectsReturned`` will catch

    :exc:`~django.db.models.Model.MultipleObjectsReturned` exceptions for all

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    models.
```

    See :meth:`~django.db.models.query.QuerySet.get()`.

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``SuspiciousOperation``
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-----------------------
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.. exception:: SuspiciousOperation
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    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. Subclasses of

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    ``SuspiciousOperation`` include:
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```
    * ``DisallowedHost``
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```
    * ``DisallowedModelAdminLookup``
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    * ``DisallowedModelAdminToField``
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    * ``DisallowedRedirect``
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    * ``InvalidSessionKey``
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    * ``RequestDataTooBig``
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    * ``SuspiciousFileOperation``
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    * ``SuspiciousMultipartForm``
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    * ``SuspiciousSession``
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    * ``TooManyFieldsSent``
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    * ``TooManyFilesSent``
```

    If a ``SuspiciousOperation`` exception reaches the ASGI/WSGI handler level

    it is logged at the ``Error`` level and results in

    a :class:`~django.http.HttpResponseBadRequest`. See the :doc:`logging

    documentation </topics/logging/>` for more information.

```
.. versionchanged:: 3.2.18
```

    ``SuspiciousOperation`` is raised when too many files are submitted.

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

    The :exc:`PermissionDenied` exception is raised when a user does not have

    permission to perform the action requested.

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``ViewDoesNotExist``
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--------------------
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```
.. exception:: ViewDoesNotExist
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    The :exc:`ViewDoesNotExist` exception is raised by

    :mod:`django.urls` when a requested view does not exist.

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``MiddlewareNotUsed``
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---------------------
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.. exception:: MiddlewareNotUsed
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    The :exc:`MiddlewareNotUsed` exception is raised when a middleware is not

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    used in the server configuration.
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``ImproperlyConfigured``
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------------------------
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.. exception:: ImproperlyConfigured
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    The :exc:`ImproperlyConfigured` exception is raised when Django is

    somehow improperly configured -- for example, if a value in ``settings.py``

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    is incorrect or unparseable.
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``FieldError``
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--------------
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```
.. exception:: FieldError
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    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

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      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

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      parameters
```

    - A join is not permitted on the specified field

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    - A field name is invalid
```

    - A query contains invalid order_by arguments

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``ValidationError``
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-------------------
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```
.. 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>`.

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``NON_FIELD_ERRORS``
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```
~~~~~~~~~~~~~~~~~~~~
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```
.. data:: NON_FIELD_ERRORS
```

``ValidationError``\s 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

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list of errors.
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``BadRequest``
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```
--------------
```
```
.. exception:: BadRequest
```

    The :exc:`BadRequest` exception is raised when the request cannot be

    processed due to a client error. If a ``BadRequest`` exception reaches the

    ASGI/WSGI handler level it results in a

    :class:`~django.http.HttpResponseBadRequest`.

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``RequestAborted``
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------------------
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```
.. exception:: RequestAborted
```

    The :exc:`RequestAborted` exception is raised when an HTTP body being read

    in by the handler is cut off midstream and the client connection closes,

    or when the client does not send data and hits a timeout where the server

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    closes the connection.
```

    It is internal to the HTTP handler modules and you are unlikely to see

    it elsewhere. If you are modifying HTTP handling code, you should raise

    this when you encounter an aborted request to make sure the socket is

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    closed cleanly.
```
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``SynchronousOnlyOperation``
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```
----------------------------
```

.. exception:: SynchronousOnlyOperation

    The :exc:`SynchronousOnlyOperation` exception is raised when code that

    is only allowed in synchronous Python code is called from an asynchronous

    context (a thread with a running asynchronous event loop). These parts of

    Django are generally heavily reliant on thread-safety to function and don't

    work correctly under coroutines sharing the same thread.

    If you are trying to call code that is synchronous-only from an

    asynchronous thread, then create a synchronous thread and call it in that.

    You can accomplish this is with :func:`asgiref.sync.sync_to_async`.

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.. currentmodule:: django.urls
```
```
URL Resolver exceptions
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```
=======================
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URL Resolver exceptions are defined in ``django.urls``.

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``Resolver404``
```
```
---------------
```
```
.. exception:: Resolver404
```

    The :exc:`Resolver404` exception is raised by

    :func:`~django.urls.resolve()` if the path passed to ``resolve()`` doesn't

    map to a view. It's a subclass of :class:`django.http.Http404`.

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``NoReverseMatch``
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```
------------------
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```
.. exception:: NoReverseMatch
```

    The :exc:`NoReverseMatch` exception is raised by :mod:`django.urls` when a

    matching URL in your URLconf cannot be identified based on the parameters

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    supplied.
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.. currentmodule:: django.db
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Database Exceptions
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===================
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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.

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.. exception:: Error
```
```
.. exception:: InterfaceError
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```
.. exception:: DatabaseError
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```
.. exception:: DataError
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.. exception:: OperationalError
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.. exception:: IntegrityError
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.. exception:: InternalError
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.. exception:: ProgrammingError
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```
.. 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.
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```
.. exception:: models.ProtectedError
```

Raised to prevent deletion of referenced objects when using

:attr:`django.db.models.PROTECT`. :exc:`models.ProtectedError` is a subclass

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of :exc:`IntegrityError`.
```
```
.. exception:: models.RestrictedError
```

Raised to prevent deletion of referenced objects when using

:attr:`django.db.models.RESTRICT`. :exc:`models.RestrictedError` is a subclass

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of :exc:`IntegrityError`.
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```
.. currentmodule:: django.http
```
```
HTTP Exceptions
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```
===============
```

HTTP exceptions may be imported from ``django.http``.

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``UnreadablePostError``
```
```
-----------------------
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```
.. exception:: UnreadablePostError
```

    :exc:`UnreadablePostError` is raised when a user cancels an upload.

.. currentmodule:: django.contrib.sessions.exceptions

```
Sessions Exceptions
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```
===================
```

Sessions exceptions are defined in ``django.contrib.sessions.exceptions``.

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``SessionInterrupted``
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```
----------------------
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```
.. exception:: SessionInterrupted
```

    :exc:`SessionInterrupted` is raised when a session is destroyed in a

    concurrent request. It's a subclass of

    :exc:`~django.core.exceptions.BadRequest`.

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Transaction Exceptions
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```
======================
```

.. currentmodule:: django.db.transaction

Transaction exceptions are defined in ``django.db.transaction``.

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``TransactionManagementError``
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```
------------------------------
```

.. exception:: TransactionManagementError

    :exc:`TransactionManagementError` is raised for any and all problems

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    related to database transactions.
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.. currentmodule:: django.test
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Testing Framework Exceptions
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============================
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Exceptions provided by the ``django.test`` package.

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``RedirectCycleError``
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```
----------------------
```

.. exception:: client.RedirectCycleError

    :exc:`~client.RedirectCycleError` is raised when the test client detects a

    loop or an overly long chain of redirects.

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Python Exceptions
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```
=================
```

Django raises built-in Python exceptions when appropriate as well. See the

Python documentation for further information on the :ref:`bltin-exceptions`.