.. _ref-contrib-admin:

=====================
The Django admin site
=====================

.. module:: django.contrib.admin
   :synopsis: Django's admin site.

.. currentmodule:: django.contrib.admin

One of the most powerful parts of Django is the automatic admin interface. It
reads metadata in your model to provide a powerful and production-ready
interface that content producers can immediately use to start adding content to
the site. In this document, we discuss how to activate, use and customize
Django's admin interface.

.. admonition:: Note

    The admin site has been refactored significantly since Django 0.96. This
    document describes the newest version of the admin site, which allows for
    much richer customization. If you follow the development of Django itself,
    you may have heard this described as "newforms-admin."

Overview
========

There are six steps in activating the Django admin site:

    1. Add ``'django.contrib.admin'`` to your :setting:`INSTALLED_APPS`
       setting.

    2. Admin has two dependencies - ``django.contrib.auth`` and
       ``django.contrib.contenttypes``. If these applications are not
       in your :setting:`INSTALLED_APPS` list, add them.

    3. Determine which of your application's models should be editable in the
       admin interface.

    4. For each of those models, optionally create a ``ModelAdmin`` class that
       encapsulates the customized admin functionality and options for that
       particular model.

    5. Instantiate an ``AdminSite`` and tell it about each of your models and
       ``ModelAdmin`` classes.

    6. Hook the ``AdminSite`` instance into your URLconf.

Other topics
------------

.. toctree::
   :maxdepth: 1

   actions

.. seealso::

    For information about serving the media files (images, JavaScript, and CSS)
    associated with the admin in production, see :ref:`serving-media-files`.

``ModelAdmin`` objects
======================

.. class:: ModelAdmin

The ``ModelAdmin`` class is the representation of a model in the admin
interface. These are stored in a file named ``admin.py`` in your application.
Let's take a look at a very simple example of the ``ModelAdmin``::

    from django.contrib import admin
    from myproject.myapp.models import Author

    class AuthorAdmin(admin.ModelAdmin):
        pass
    admin.site.register(Author, AuthorAdmin)

.. admonition:: Do you need a ``ModelAdmin`` object at all?

    In the preceding example, the ``ModelAdmin`` class doesn't define any
    custom values (yet). As a result, the default admin interface will be
    provided. If you are happy with the default admin interface, you don't
    need to define a ``ModelAdmin`` object at all -- you can register the
    model class without providing a ``ModelAdmin`` description. The
    preceding example could be simplified to::

        from django.contrib import admin
        from myproject.myapp.models import Author

        admin.site.register(Author)

``ModelAdmin`` Options
----------------------

The ``ModelAdmin`` is very flexible. It has several options for dealing with
customizing the interface. All options are defined on the ``ModelAdmin``
subclass::

    class AuthorAdmin(admin.ModelAdmin):
        date_hierarchy = 'pub_date'

.. attribute:: ModelAdmin.date_hierarchy

Set ``date_hierarchy`` to the name of a ``DateField`` or ``DateTimeField`` in
your model, and the change list page will include a date-based drilldown
navigation by that field.

Example::

    date_hierarchy = 'pub_date'

.. attribute:: ModelAdmin.form

By default a ``ModelForm`` is dynamically created for your model. It is used
to create the form presented on both the add/change pages. You can easily
provide your own ``ModelForm`` to override any default form behavior on the
add/change pages.

For an example see the section `Adding custom validation to the admin`_.

.. attribute:: ModelAdmin.fieldsets

Set ``fieldsets`` to control the layout of admin "add" and "change" pages.

``fieldsets`` is a list of two-tuples, in which each two-tuple represents a
``<fieldset>`` on the admin form page. (A ``<fieldset>`` is a "section" of the
form.)

The two-tuples are in the format ``(name, field_options)``, where ``name`` is a
string representing the title of the fieldset and ``field_options`` is a
dictionary of information about the fieldset, including a list of fields to be
displayed in it.

A full example, taken from the ``django.contrib.flatpages.FlatPage`` model::

    class FlatPageAdmin(admin.ModelAdmin):
        fieldsets = (
            (None, {
                'fields': ('url', 'title', 'content', 'sites')
            }),
            ('Advanced options', {
                'classes': ('collapse',),
                'fields': ('enable_comments', 'registration_required', 'template_name')
            }),
        )

This results in an admin page that looks like:

    .. image:: _images/flatfiles_admin.png

If ``fieldsets`` isn't given, Django will default to displaying each field
that isn't an ``AutoField`` and has ``editable=True``, in a single fieldset,
in the same order as the fields are defined in the model.

The ``field_options`` dictionary can have the following keys:

    * ``fields``
        A tuple of field names to display in this fieldset. This key is
        required.

        Example::

            {
            'fields': ('first_name', 'last_name', 'address', 'city', 'state'),
            }

        To display multiple fields on the same line, wrap those fields in
        their own tuple. In this example, the ``first_name`` and ``last_name``
        fields will display on the same line::

            {
            'fields': (('first_name', 'last_name'), 'address', 'city', 'state'),
            }

        .. versionadded:: 1.2

        ``fields`` can contain values defined in
        :attr:`ModelAdmin.readonly_fields` to be displayed as read-only.

    * ``classes``
        A list containing extra CSS classes to apply to the fieldset.

        Example::

            {
            'classes': ['wide', 'extrapretty'],
            }

        Two useful classes defined by the default admin site stylesheet are
        ``collapse`` and ``wide``. Fieldsets with the ``collapse`` style will
        be initially collapsed in the admin and replaced with a small
        "click to expand" link. Fieldsets with the ``wide`` style will be
        given extra horizontal space.

    * ``description``
        A string of optional extra text to be displayed at the top of each
        fieldset, under the heading of the fieldset.

        Note that this value is *not* HTML-escaped when it's displayed in
        the admin interface. This lets you include HTML if you so desire.
        Alternatively you can use plain text and
        ``django.utils.html.escape()`` to escape any HTML special
        characters.

.. attribute:: ModelAdmin.fields

Use this option as an alternative to ``fieldsets`` if the layout does not
matter and if you want to only show a subset of the available fields in the
form. For example, you could define a simpler version of the admin form for
the ``django.contrib.flatpages.FlatPage`` model as follows::

    class FlatPageAdmin(admin.ModelAdmin):
        fields = ('url', 'title', 'content')

In the above example, only the fields 'url', 'title' and 'content' will be
displayed, sequentially, in the form.

.. versionadded:: 1.2

``fields`` can contain values defined in :attr:`ModelAdmin.readonly_fields`
to be displayed as read-only.

.. admonition:: Note

    This ``fields`` option should not be confused with the ``fields``
    dictionary key that is within the ``fieldsets`` option, as described in
    the previous section.

.. attribute:: ModelAdmin.exclude

This attribute, if given, should be a list of field names to exclude from the
form.

For example, let's consider the following model::

    class Author(models.Model):
        name = models.CharField(max_length=100)
        title = models.CharField(max_length=3)
        birth_date = models.DateField(blank=True, null=True)

If you want a form for the ``Author`` model that includes only the ``name``
and ``title`` fields, you would specify ``fields`` or ``exclude`` like this::

    class AuthorAdmin(admin.ModelAdmin):
        fields = ('name', 'title')

    class AuthorAdmin(admin.ModelAdmin):
        exclude = ('birth_date',)

Since the Author model only has three fields, ``name``, ``title``, and
``birth_date``, the forms resulting from the above declarations will contain
exactly the same fields.

.. attribute:: ModelAdmin.filter_horizontal

Use a nifty unobtrusive JavaScript "filter" interface instead of the
usability-challenged ``<select multiple>`` in the admin form. The value is a
list of fields that should be displayed as a horizontal filter interface. See
``filter_vertical`` to use a vertical interface.

.. attribute:: ModelAdmin.filter_vertical

Same as ``filter_horizontal``, but is a vertical display of the filter
interface.

.. attribute:: ModelAdmin.list_display

Set ``list_display`` to control which fields are displayed on the change list
page of the admin.

Example::

    list_display = ('first_name', 'last_name')

If you don't set ``list_display``, the admin site will display a single column
that displays the ``__unicode__()`` representation of each object.

You have four possible values that can be used in ``list_display``:

    * A field of the model. For example::

          class PersonAdmin(admin.ModelAdmin):
              list_display = ('first_name', 'last_name')

    * A callable that accepts one parameter for the model instance. For
      example::

          def upper_case_name(obj):
              return ("%s %s" % (obj.first_name, obj.last_name)).upper()
          upper_case_name.short_description = 'Name'

          class PersonAdmin(admin.ModelAdmin):
              list_display = (upper_case_name,)

    * A string representing an attribute on the ``ModelAdmin``. This behaves
      same as the callable. For example::

          class PersonAdmin(admin.ModelAdmin):
              list_display = ('upper_case_name',)

              def upper_case_name(self, obj):
                return ("%s %s" % (obj.first_name, obj.last_name)).upper()
              upper_case_name.short_description = 'Name'

    * A string representing an attribute on the model. This behaves almost
      the same as the callable, but ``self`` in this context is the model
      instance. Here's a full model example::

          class Person(models.Model):
              name = models.CharField(max_length=50)
              birthday = models.DateField()

              def decade_born_in(self):
                  return self.birthday.strftime('%Y')[:3] + "0's"
              decade_born_in.short_description = 'Birth decade'

          class PersonAdmin(admin.ModelAdmin):
              list_display = ('name', 'decade_born_in')

A few special cases to note about ``list_display``:

    * If the field is a ``ForeignKey``, Django will display the
      ``__unicode__()`` of the related object.

    * ``ManyToManyField`` fields aren't supported, because that would entail
      executing a separate SQL statement for each row in the table. If you
      want to do this nonetheless, give your model a custom method, and add
      that method's name to ``list_display``. (See below for more on custom
      methods in ``list_display``.)

    * If the field is a ``BooleanField`` or ``NullBooleanField``, Django will
      display a pretty "on" or "off" icon instead of ``True`` or ``False``.

    * If the string given is a method of the model, ``ModelAdmin`` or a
      callable, Django will HTML-escape the output by default. If you'd rather
      not escape the output of the method, give the method an ``allow_tags``
      attribute whose value is ``True``.

      Here's a full example model::

          class Person(models.Model):
              first_name = models.CharField(max_length=50)
              last_name = models.CharField(max_length=50)
              color_code = models.CharField(max_length=6)

              def colored_name(self):
                  return '<span style="color: #%s;">%s %s</span>' % (self.color_code, self.first_name, self.last_name)
              colored_name.allow_tags = True

          class PersonAdmin(admin.ModelAdmin):
              list_display = ('first_name', 'last_name', 'colored_name')

    * If the string given is a method of the model, ``ModelAdmin`` or a
      callable that returns True or False Django will display a pretty "on" or
      "off" icon if you give the method a ``boolean`` attribute whose value is
      ``True``.

      Here's a full example model::

          class Person(models.Model):
              first_name = models.CharField(max_length=50)
              birthday = models.DateField()

              def born_in_fifties(self):
                  return self.birthday.strftime('%Y')[:3] == '195'
              born_in_fifties.boolean = True

          class PersonAdmin(admin.ModelAdmin):
              list_display = ('name', 'born_in_fifties')


    * The ``__str__()`` and ``__unicode__()`` methods are just as valid in
      ``list_display`` as any other model method, so it's perfectly OK to do
      this::

          list_display = ('__unicode__', 'some_other_field')

    * Usually, elements of ``list_display`` that aren't actual database fields
      can't be used in sorting (because Django does all the sorting at the
      database level).

      However, if an element of ``list_display`` represents a certain database
      field, you can indicate this fact by setting the ``admin_order_field``
      attribute of the item.

      For example::

        class Person(models.Model):
            first_name = models.CharField(max_length=50)
            color_code = models.CharField(max_length=6)

            def colored_first_name(self):
                return '<span style="color: #%s;">%s</span>' % (self.color_code, self.first_name)
            colored_first_name.allow_tags = True
            colored_first_name.admin_order_field = 'first_name'

        class PersonAdmin(admin.ModelAdmin):
            list_display = ('first_name', 'colored_first_name')

      The above will tell Django to order by the ``first_name`` field when
      trying to sort by ``colored_first_name`` in the admin.

.. attribute:: ModelAdmin.list_display_links

Set ``list_display_links`` to control which fields in ``list_display`` should
be linked to the "change" page for an object.

By default, the change list page will link the first column -- the first field
specified in ``list_display`` -- to the change page for each item. But
``list_display_links`` lets you change which columns are linked. Set
``list_display_links`` to a list or tuple of field names (in the same format as
``list_display``) to link.

``list_display_links`` can specify one or many field names. As long as the
field names appear in ``list_display``, Django doesn't care how many (or how
few) fields are linked. The only requirement is: If you want to use
``list_display_links``, you must define ``list_display``.

In this example, the ``first_name`` and ``last_name`` fields will be linked on
the change list page::

    class PersonAdmin(admin.ModelAdmin):
        list_display = ('first_name', 'last_name', 'birthday')
        list_display_links = ('first_name', 'last_name')

.. _admin-list-editable:

.. attribute:: ModelAdmin.list_editable

.. versionadded:: 1.1

Set ``list_editable`` to a list of field names on the model which will allow
editing on the change list page. That is, fields listed in ``list_editable``
will be displayed as form widgets on the change list page, allowing users to
edit and save multiple rows at once.

.. note::

    ``list_editable`` interacts with a couple of other options in particular
    ways; you should note the following rules:

        * Any field in ``list_editable`` must also be in ``list_display``. You
          can't edit a field that's not displayed!

        * The same field can't be listed in both ``list_editable`` and
          ``list_display_links`` -- a field can't be both a form and a link.

    You'll get a validation error if either of these rules are broken.

.. attribute:: ModelAdmin.list_filter

Set ``list_filter`` to activate filters in the right sidebar of the change list
page of the admin. This should be a list of field names, and each specified
field should be either a ``BooleanField``, ``CharField``, ``DateField``,
``DateTimeField``, ``IntegerField`` or ``ForeignKey``.

This example, taken from the ``django.contrib.auth.models.User`` model, shows
how both ``list_display`` and ``list_filter`` work::

    class UserAdmin(admin.ModelAdmin):
        list_display = ('username', 'email', 'first_name', 'last_name', 'is_staff')
        list_filter = ('is_staff', 'is_superuser')

The above code results in an admin change list page that looks like this:

    .. image:: _images/users_changelist.png

(This example also has ``search_fields`` defined. See below.)

.. attribute:: ModelAdmin.list_per_page

Set ``list_per_page`` to control how many items appear on each paginated admin
change list page. By default, this is set to ``100``.

.. attribute:: ModelAdmin.list_select_related

Set ``list_select_related`` to tell Django to use ``select_related()`` in
retrieving the list of objects on the admin change list page. This can save you
a bunch of database queries.

The value should be either ``True`` or ``False``. Default is ``False``.

Note that Django will use ``select_related()``, regardless of this setting,
if one of the ``list_display`` fields is a ``ForeignKey``.

For more on ``select_related()``, see
:ref:`the select_related() docs <select-related>`.

.. attribute:: ModelAdmin.inlines

See ``InlineModelAdmin`` objects below.

.. attribute:: ModelAdmin.ordering

Set ``ordering`` to specify how objects on the admin change list page should be
ordered. This should be a list or tuple in the same format as a model's
``ordering`` parameter.

If this isn't provided, the Django admin will use the model's default ordering.

.. admonition:: Note

    Django will only honor the first element in the list/tuple; any others
    will be ignored.

.. attribute:: ModelAdmin.prepopulated_fields

Set ``prepopulated_fields`` to a dictionary mapping field names to the fields
it should prepopulate from::

    class ArticleAdmin(admin.ModelAdmin):
        prepopulated_fields = {"slug": ("title",)}

When set, the given fields will use a bit of JavaScript to populate from the
fields assigned. The main use for this functionality is to automatically
generate the value for ``SlugField`` fields from one or more other fields. The
generated value is produced by concatenating the values of the source fields,
and then by transforming that result into a valid slug (e.g. substituting
dashes for spaces).

``prepopulated_fields`` doesn't accept ``DateTimeField``, ``ForeignKey``, nor
``ManyToManyField`` fields.

.. attribute:: ModelAdmin.radio_fields

By default, Django's admin uses a select-box interface (<select>) for
fields that are ``ForeignKey`` or have ``choices`` set. If a field is present
in ``radio_fields``, Django will use a radio-button interface instead.
Assuming ``group`` is a ``ForeignKey`` on the ``Person`` model::

    class PersonAdmin(admin.ModelAdmin):
        radio_fields = {"group": admin.VERTICAL}

You have the choice of using ``HORIZONTAL`` or ``VERTICAL`` from the
``django.contrib.admin`` module.

Don't include a field in ``radio_fields`` unless it's a ``ForeignKey`` or has
``choices`` set.

.. attribute:: ModelAdmin.raw_id_fields

By default, Django's admin uses a select-box interface (<select>) for
fields that are ``ForeignKey``. Sometimes you don't want to incur the
overhead of having to select all the related instances to display in the
drop-down.

``raw_id_fields`` is a list of fields you would like to change
into a ``Input`` widget for either a ``ForeignKey`` or ``ManyToManyField``::

    class ArticleAdmin(admin.ModelAdmin):
        raw_id_fields = ("newspaper",)

.. attribute:: ModelAdmin.readonly_fields

.. versionadded:: 1.2

By default the admin shows all fields as editable. Any fields in this option
(which should be a ``list`` or ``tuple``) will display its data as-is and
non-editable. This option behaves nearly identical to :attr:`ModelAdmin.list_display`.
Usage is the same, however, when you specify :attr:`ModelAdmin.fields` or
:attr:`ModelAdmin.fieldsets` the read-only fields must be present to be shown
(they are ignored otherwise).

If ``readonly_fields`` is used without defining explicit ordering through
:attr:`ModelAdmin.fields` or :attr:`ModelAdmin.fieldsets` they will be added
last after all editable fields.

.. attribute:: ModelAdmin.save_as

Set ``save_as`` to enable a "save as" feature on admin change forms.

Normally, objects have three save options: "Save", "Save and continue editing"
and "Save and add another". If ``save_as`` is ``True``, "Save and add another"
will be replaced by a "Save as" button.

"Save as" means the object will be saved as a new object (with a new ID),
rather than the old object.

By default, ``save_as`` is set to ``False``.

.. attribute:: ModelAdmin.save_on_top

Set ``save_on_top`` to add save buttons across the top of your admin change
forms.

Normally, the save buttons appear only at the bottom of the forms. If you set
``save_on_top``, the buttons will appear both on the top and the bottom.

By default, ``save_on_top`` is set to ``False``.

.. attribute:: ModelAdmin.search_fields

Set ``search_fields`` to enable a search box on the admin change list page.
This should be set to a list of field names that will be searched whenever
somebody submits a search query in that text box.

These fields should be some kind of text field, such as ``CharField`` or
``TextField``. You can also perform a related lookup on a ``ForeignKey`` with
the lookup API "follow" notation::

    search_fields = ['foreign_key__related_fieldname']

When somebody does a search in the admin search box, Django splits the search
query into words and returns all objects that contain each of the words, case
insensitive, where each word must be in at least one of ``search_fields``. For
example, if ``search_fields`` is set to ``['first_name', 'last_name']`` and a
user searches for ``john lennon``, Django will do the equivalent of this SQL
``WHERE`` clause::

    WHERE (first_name ILIKE '%john%' OR last_name ILIKE '%john%')
    AND (first_name ILIKE '%lennon%' OR last_name ILIKE '%lennon%')

For faster and/or more restrictive searches, prefix the field name
with an operator:

``^``
    Matches the beginning of the field. For example, if ``search_fields`` is
    set to ``['^first_name', '^last_name']`` and a user searches for
    ``john lennon``, Django will do the equivalent of this SQL ``WHERE``
    clause::

        WHERE (first_name ILIKE 'john%' OR last_name ILIKE 'john%')
        AND (first_name ILIKE 'lennon%' OR last_name ILIKE 'lennon%')

    This query is more efficient than the normal ``'%john%'`` query, because
    the database only needs to check the beginning of a column's data, rather
    than seeking through the entire column's data. Plus, if the column has an
    index on it, some databases may be able to use the index for this query,
    even though it's a ``LIKE`` query.

``=``
    Matches exactly, case-insensitive. For example, if
    ``search_fields`` is set to ``['=first_name', '=last_name']`` and
    a user searches for ``john lennon``, Django will do the equivalent
    of this SQL ``WHERE`` clause::

        WHERE (first_name ILIKE 'john' OR last_name ILIKE 'john')
        AND (first_name ILIKE 'lennon' OR last_name ILIKE 'lennon')

    Note that the query input is split by spaces, so, following this example,
    it's currently not possible to search for all records in which
    ``first_name`` is exactly ``'john winston'`` (containing a space).

``@``
    Performs a full-text match. This is like the default search method but uses
    an index. Currently this is only available for MySQL.

.. attribute:: ModelAdmin.formfield_overrides

.. versionadded:: 1.1

This provides a quick-and-dirty way to override some of the
:class:`~django.forms.Field` options for use in the admin.
``formfield_overrides`` is a dictionary mapping a field class to a dict of
arguments to pass to the field at construction time.

Since that's a bit abstract, let's look at a concrete example. The most common
use of ``formfield_overrides`` is to add a custom widget for a certain type of
field. So, imagine we've written a ``RichTextEditorWidget`` that we'd like to
use for large text fields instead of the default ``<textarea>``. Here's how we'd
do that::

    from django.db import models
    from django.contrib import admin

    # Import our custom widget and our model from where they're defined
    from myapp.widgets import RichTextEditorWidget
    from myapp.models import MyModel

    class MyModelAdmin(admin.ModelAdmin):
        formfield_overrides = {
            models.TextField: {'widget': RichTextEditorWidget},
        }

Note that the key in the dictionary is the actual field class, *not* a string.
The value is another dictionary; these arguments will be passed to
:meth:`~django.forms.Field.__init__`. See :ref:`ref-forms-api` for details.

.. warning::

    If you want to use a custom widget with a relation field (i.e.
    :class:`~django.db.models.ForeignKey` or
    :class:`~django.db.models.ManyToManyField`), make sure you haven't included
    that field's name in ``raw_id_fields`` or ``radio_fields``.

    ``formfield_overrides`` won't let you change the widget on relation fields
    that have ``raw_id_fields`` or ``radio_fields`` set. That's because
    ``raw_id_fields`` and ``radio_fields`` imply custom widgets of their own.

.. attribute:: ModelAdmin.actions

.. versionadded:: 1.1

A list of actions to make available on the change list page. See
:ref:`ref-contrib-admin-actions` for details.

.. attribute:: ModelAdmin.actions_on_top
.. attribute:: ModelAdmin.actions_on_bottom

.. versionadded:: 1.1

Controls where on the page the actions bar appears. By default, the admin
changelist displays actions at the top of the page (``actions_on_top = True;
actions_on_bottom = False``).

.. attribute:: ModelAdmin.actions_selection_counter

.. versionadded:: 1.2

Controls whether a selection counter is display next to the action dropdown.
By default, the admin changelist will display it
(``actions_selection_counter = True``).

.. attribute:: ModelAdmin.change_list_template

Path to a custom template that will be used by the model objects "change list"
view. Templates can override or extend base admin templates as described in
`Overriding Admin Templates`_.

If you don't specify this attribute, a default template shipped with Django
that provides the standard appearance is used.

.. attribute:: ModelAdmin.add_form_template

.. versionadded:: 1.2

Path to a custom template that will be used by the model object creation
views. Templates can override or extend base admin templates as described in
`Overriding Admin Templates`_.

If you don't specify this attribute, a default template shipped with Django
that provides the standard appearance is used.

.. attribute:: ModelAdmin.change_form_template

Path to a custom template that will be used by the model object change views.
Templates can override or extend base admin templates as described in
`Overriding Admin Templates`_.

If you don't specify this attribute, a default template shipped with Django
that provides the standard appearance is used.

.. attribute:: ModelAdmin.object_history_template

Path to a custom template that will be used by the model object change history
display view. Templates can override or extend base admin templates as
described in `Overriding Admin Templates`_.

If you don't specify this attribute, a default template shipped with Django
that provides the standard appearance is used.

.. attribute:: ModelAdmin.delete_confirmation_template

Path to a custom template that will be used by the view responsible of showing
the confirmation page when the user decides to delete one or more model
objects. Templates can override or extend base admin templates as described in
`Overriding Admin Templates`_.

If you don't specify this attribute, a default template shipped with Django
that provides the standard appearance is used.

.. _model-admin-methods:

``ModelAdmin`` methods
----------------------

.. method:: ModelAdmin.save_model(self, request, obj, form, change)

The ``save_model`` method is given the ``HttpRequest``, a model instance,
a ``ModelForm`` instance and a boolean value based on whether it is adding or
changing the object. Here you can do any pre- or post-save operations.

For example to attach ``request.user`` to the object prior to saving::

    class ArticleAdmin(admin.ModelAdmin):
        def save_model(self, request, obj, form, change):
            obj.user = request.user
            obj.save()

.. method:: ModelAdmin.save_formset(self, request, form, formset, change)

The ``save_formset`` method is given the ``HttpRequest``, the parent
``ModelForm`` instance and a boolean value based on whether it is adding or
changing the parent object.

For example to attach ``request.user`` to each changed formset
model instance::

    class ArticleAdmin(admin.ModelAdmin):
        def save_formset(self, request, form, formset, change):
            instances = formset.save(commit=False)
            for instance in instances:
                instance.user = request.user
                instance.save()
            formset.save_m2m()

.. method:: ModelAdmin.get_readonly_fields(self, request, obj=None)

.. versionadded:: 1.2

The ``get_readonly_fields`` method is given the ``HttpRequest`` and the
``obj`` being edited (or ``None`` on an add form) and is expected to return a
``list`` or ``tuple`` of field names that will be displayed as read-only, as
described above in the :attr:`ModelAdmin.readonly_fields` section.

.. method:: ModelAdmin.get_urls(self)

.. versionadded:: 1.1

The ``get_urls`` method on a ``ModelAdmin`` returns the URLs to be used for
that ModelAdmin in the same way as a URLconf.  Therefore you can extend them as
documented in :ref:`topics-http-urls`::

    class MyModelAdmin(admin.ModelAdmin):
        def get_urls(self):
            urls = super(MyModelAdmin, self).get_urls()
            my_urls = patterns('',
                (r'^my_view/$', self.my_view)
            )
            return my_urls + urls

.. note::

    Notice that the custom patterns are included *before* the regular admin
    URLs: the admin URL patterns are very permissive and will match nearly
    anything, so you'll usually want to prepend your custom URLs to the built-in
    ones.

However, the ``self.my_view`` function registered above suffers from two
problems:

  * It will *not* perform any permission checks, so it will be accessible to
    the general public.
  * It will *not* provide any header details to prevent caching. This means if
    the page retrieves data from the database, and caching middleware is
    active, the page could show outdated information.

Since this is usually not what you want, Django provides a convenience wrapper
to check permissions and mark the view as non-cacheable. This wrapper is
:meth:`AdminSite.admin_view` (i.e.  ``self.admin_site.admin_view`` inside a
``ModelAdmin`` instance); use it like so::

    class MyModelAdmin(admin.ModelAdmin):
        def get_urls(self):
            urls = super(MyModelAdmin, self).get_urls()
            my_urls = patterns('',
                (r'^my_view/$', self.admin_site.admin_view(self.my_view))
            )
            return my_urls + urls

Notice the wrapped view in the fifth line above::

    (r'^my_view/$', self.admin_site.admin_view(self.my_view))

This wrapping will protect ``self.my_view`` from unauthorized access and will
apply the ``django.views.decorators.cache.never_cache`` decorator to make sure
it is not cached if the cache middleware is active.

If the page is cacheable, but you still want the permission check to be performed,
you can pass a ``cacheable=True`` argument to :meth:`AdminSite.admin_view`::

    (r'^my_view/$', self.admin_site.admin_view(self.my_view, cacheable=True))

.. method:: ModelAdmin.formfield_for_foreignkey(self, db_field, request, **kwargs)

.. versionadded:: 1.1

The ``formfield_for_foreignkey`` method on a ``ModelAdmin`` allows you to
override the default formfield for a foreign key field. For example, to
return a subset of objects for this foreign key field based on the user::

    class MyModelAdmin(admin.ModelAdmin):
        def formfield_for_foreignkey(self, db_field, request, **kwargs):
            if db_field.name == "car":
                kwargs["queryset"] = Car.objects.filter(owner=request.user)
                return db_field.formfield(**kwargs)
            return super(MyModelAdmin, self).formfield_for_foreignkey(db_field, request, **kwargs)

This uses the ``HttpRequest`` instance to filter the ``Car`` foreign key field
to only the cars owned by the ``User`` instance.

Other methods
~~~~~~~~~~~~~

.. method:: ModelAdmin.add_view(self, request, form_url='', extra_context=None)

Django view for the model instance addition page. See note below.

.. method:: ModelAdmin.change_view(self, request, object_id, extra_context=None)

Django view for the model instance edition page. See note below.

.. method:: ModelAdmin.changelist_view(self, request, extra_context=None)

Django view for the model instances change list/actions page. See note below.

.. method:: ModelAdmin.delete_view(self, request, object_id, extra_context=None)

Django view for the model instance(s) deletion confirmation page. See note below.

.. method:: ModelAdmin.history_view(self, request, object_id, extra_context=None)

Django view for the page that shows the modification history for a given model
instance.

Unlike the hook-type ``ModelAdmin`` methods detailed in the previous section,
these five methods are in reality designed to be invoked as Django views from
the admin application URL dispatching handler to render the pages that deal
with model instances CRUD operations. As a result, completely overriding these
methods will significantly change the behavior of the admin application.

One common reason for overriding these methods is to augment the context data
that is provided to the template that renders the view. In the following
example, the change view is overridden so that the rendered template is
provided some extra mapping data that would not otherwise be available::

    class MyModelAdmin(admin.ModelAdmin):

        # A template for a very customized change view:
        change_form_template = 'admin/myapp/extras/openstreetmap_change_form.html'

        def get_osm_info(self):
            # ...

        def change_view(self, request, object_id, extra_context=None):
            my_context = {
                'osm_data': self.get_osm_info(),
            }
            return super(MyModelAdmin, self).change_view(request, object_id,
                extra_context=my_context)

``ModelAdmin`` media definitions
--------------------------------

There are times where you would like add a bit of CSS and/or JavaScript to
the add/change views. This can be accomplished by using a Media inner class
on your ``ModelAdmin``::

    class ArticleAdmin(admin.ModelAdmin):
        class Media:
            css = {
                "all": ("my_styles.css",)
            }
            js = ("my_code.js",)

Keep in mind that this will be prepended with ``MEDIA_URL``. The same rules
apply as :ref:`regular media definitions on forms <topics-forms-media>`.

Adding custom validation to the admin
-------------------------------------

Adding custom validation of data in the admin is quite easy. The automatic admin
interface reuses :mod:`django.forms`, and the ``ModelAdmin`` class gives you
the ability define your own form::

    class ArticleAdmin(admin.ModelAdmin):
        form = MyArticleAdminForm

``MyArticleAdminForm`` can be defined anywhere as long as you import where
needed. Now within your form you can add your own custom validation for
any field::

    class MyArticleAdminForm(forms.ModelForm):
        class Meta:
            model = Article

        def clean_name(self):
            # do something that validates your data
            return self.cleaned_data["name"]

It is important you use a ``ModelForm`` here otherwise things can break. See the
:ref:`forms <ref-forms-index>` documentation on :ref:`custom validation
<ref-forms-validation>` and, more specifically, the
:ref:`model form validation notes <overriding-modelform-clean-method>` for more
information.

.. _admin-inlines:

``InlineModelAdmin`` objects
============================

The admin interface has the ability to edit models on the same page as a
parent model. These are called inlines. Suppose you have these two models::

     class Author(models.Model):
        name = models.CharField(max_length=100)

     class Book(models.Model):
        author = models.ForeignKey(Author)
        title = models.CharField(max_length=100)

You can edit the books authored by an author on the author page. You add
inlines to a model by specifying them in a ``ModelAdmin.inlines``::

    class BookInline(admin.TabularInline):
        model = Book

    class AuthorAdmin(admin.ModelAdmin):
        inlines = [
            BookInline,
        ]

Django provides two subclasses of ``InlineModelAdmin`` and they are:

    * ``TabularInline``
    * ``StackedInline``

The difference between these two is merely the template used to render them.

``InlineModelAdmin`` options
-----------------------------

The ``InlineModelAdmin`` class is a subclass of ``ModelAdmin`` so it inherits
all the same functionality as well as some of its own:

``model``
~~~~~~~~~

The model in which the inline is using. This is required.

``fk_name``
~~~~~~~~~~~

The name of the foreign key on the model. In most cases this will be dealt
with automatically, but ``fk_name`` must be specified explicitly if there are
more than one foreign key to the same parent model.

``formset``
~~~~~~~~~~~

This defaults to ``BaseInlineFormSet``. Using your own formset can give you
many possibilities of customization. Inlines are built around
:ref:`model formsets <model-formsets>`.

``form``
~~~~~~~~

The value for ``form`` defaults to ``BaseModelForm``. This is what is
passed through to ``inlineformset_factory`` when creating the formset for this
inline.

``extra``
~~~~~~~~~

This controls the number of extra forms the formset will display in addition
to the initial forms. See the
:ref:`formsets documentation <topics-forms-formsets>` for more information.

.. versionadded:: 1.2

Extra forms for inlines will be hidden and replaced with a link to dynamically
add any number of new inlines for users with Javascript enabled.

``max_num``
~~~~~~~~~~~

This controls the maximum number of forms to show in the inline. This doesn't
directly correlate to the number of objects, but can if the value is small
enough. See :ref:`model-formsets-max-num` for more information.

``raw_id_fields``
~~~~~~~~~~~~~~~~~

By default, Django's admin uses a select-box interface (<select>) for
fields that are ``ForeignKey``. Sometimes you don't want to incur the
overhead of having to select all the related instances to display in the
drop-down.

``raw_id_fields`` is a list of fields you would like to change
into a ``Input`` widget for either a ``ForeignKey`` or ``ManyToManyField``::

    class BookInline(admin.TabularInline):
        model = Book
        raw_id_fields = ("pages",)

``template``
~~~~~~~~~~~~

The template used to render the inline on the page.

``verbose_name``
~~~~~~~~~~~~~~~~

An override to the ``verbose_name`` found in the model's inner ``Meta`` class.

``verbose_name_plural``
~~~~~~~~~~~~~~~~~~~~~~~

An override to the ``verbose_name_plural`` found in the model's inner ``Meta``
class.

Working with a model with two or more foreign keys to the same parent model
---------------------------------------------------------------------------

It is sometimes possible to have more than one foreign key to the same model.
Take this model for instance::

    class Friendship(models.Model):
        to_person = models.ForeignKey(Person, related_name="friends")
        from_person = models.ForeignKey(Person, related_name="from_friends")

If you wanted to display an inline on the ``Person`` admin add/change pages
you need to explicitly define the foreign key since it is unable to do so
automatically::

    class FriendshipInline(admin.TabularInline):
        model = Friendship
        fk_name = "to_person"

    class PersonAdmin(admin.ModelAdmin):
        inlines = [
            FriendshipInline,
        ]

Working with Many-to-Many Models
--------------------------------

.. versionadded:: 1.2

By default, admin widgets for many-to-many relations will be displayed
on whichever model contains the actual reference to the ``ManyToManyField``.
Depending on your ``ModelAdmin`` definition, each many-to-many field in your
model will be represented by a standard HTML ``<select multiple>``, a
horizontal or vertical filter, or a ``raw_id_admin`` widget. However, it is
also possible to to replace these widgets with inlines.

Suppose we have the following models::

    class Person(models.Model):
        name = models.CharField(max_length=128)

    class Group(models.Model):
        name = models.CharField(max_length=128)
        members = models.ManyToManyField(Person, related_name='groups')

If you want to display many-to-many relations using an inline, you can do
so by defining an ``InlineModelAdmin`` object for the relationship::

    class MembershipInline(admin.TabularInline):
        model = Group.members.through

    class PersonAdmin(admin.ModelAdmin):
        inlines = [
            MembershipInline,
        ]

    class GroupAdmin(admin.ModelAdmin):
        inlines = [
            MembershipInline,
        ]
        exclude = ('members',)

There are two features worth noting in this example.

Firstly - the ``MembershipInline`` class references ``Group.members.through``.
The ``through`` attribute is a reference to the model that manages the
many-to-many relation. This model is automatically created by Django when you
define a many-to-many field.

Secondly, the ``GroupAdmin`` must manually exclude the ``members`` field.
Django displays an admin widget for a many-to-many field on the model that
defines the relation (in this case, ``Group``). If you want to use an inline
model to represent the many-to-many relationship, you must tell Django's admin
to *not* display this widget - otherwise you will end up with two widgets on
your admin page for managing the relation.

In all other respects, the ``InlineModelAdmin`` is exactly the same as any
other. You can customize the appearance using any of the normal
``InlineModelAdmin`` properties.

Working with Many-to-Many Intermediary Models
----------------------------------------------

When you specify an intermediary model using the ``through`` argument to a
``ManyToManyField``, the admin will not display a widget by default. This is
because each instance of that intermediary model requires more information
than could be displayed in a single widget, and the layout required for
multiple widgets will vary depending on the intermediate model.

However, we still want to be able to edit that information inline. Fortunately,
this is easy to do with inline admin models. Suppose we have the following
models::

    class Person(models.Model):
        name = models.CharField(max_length=128)

    class Group(models.Model):
        name = models.CharField(max_length=128)
        members = models.ManyToManyField(Person, through='Membership')

    class Membership(models.Model):
        person = models.ForeignKey(Person)
        group = models.ForeignKey(Group)
        date_joined = models.DateField()
        invite_reason = models.CharField(max_length=64)

The first step in displaying this intermediate model in the admin is to
define an inline class for the ``Membership`` model::

    class MembershipInline(admin.TabularInline):
        model = Membership
        extra = 1

This simple example uses the default ``InlineModelAdmin`` values for the
``Membership`` model, and limits the extra add forms to one. This could be
customized using any of the options available to ``InlineModelAdmin`` classes.

Now create admin views for the ``Person`` and ``Group`` models::

    class PersonAdmin(admin.ModelAdmin):
        inlines = (MembershipInline,)

    class GroupAdmin(admin.ModelAdmin):
        inlines = (MembershipInline,)

Finally, register your ``Person`` and ``Group`` models with the admin site::

    admin.site.register(Person, PersonAdmin)
    admin.site.register(Group, GroupAdmin)

Now your admin site is set up to edit ``Membership`` objects inline from
either the ``Person`` or the ``Group`` detail pages.

Using generic relations as an inline
------------------------------------

It is possible to use an inline with generically related objects. Let's say
you have the following models::

    class Image(models.Model):
        image = models.ImageField(upload_to="images")
        content_type = models.ForeignKey(ContentType)
        object_id = models.PositiveIntegerField()
        content_object = generic.GenericForeignKey("content_type", "object_id")

    class Product(models.Model):
        name = models.CharField(max_length=100)

If you want to allow editing and creating ``Image`` instance on the ``Product``
add/change views you can simply use ``GenericInlineModelAdmin`` provided by
``django.contrib.contenttypes.generic``. In your ``admin.py`` for this
example app::

    from django.contrib import admin
    from django.contrib.contenttypes import generic

    from myproject.myapp.models import Image, Product

    class ImageInline(generic.GenericTabularInline):
        model = Image

    class ProductAdmin(admin.ModelAdmin):
        inlines = [
            ImageInline,
        ]

    admin.site.register(Product, ProductAdmin)

``django.contrib.contenttypes.generic`` provides both a ``GenericTabularInline``
and ``GenericStackedInline`` and behave just like any other inline. See the
:ref:`contenttypes documentation <ref-contrib-contenttypes>` for more specific
information.

Overriding Admin Templates
==========================

It is relatively easy to override many of the templates which the admin module
uses to generate the various pages of an admin site. You can even override a few
of these templates for a specific app, or a specific model.

Set up your projects admin template directories
-----------------------------------------------

The admin template files are located in the ``contrib/admin/templates/admin``
directory.

In order to override one or more of them, first create an ``admin`` directory in
your project's ``templates`` directory. This can be any of the directories you
specified in ``TEMPLATE_DIRS``.

Within this ``admin`` directory, create sub-directories named after your app.
Within these app subdirectories create sub-directories named after your models.
Note, that the admin app will lowercase the model name when looking for the
directory, so make sure you name the directory in all lowercase if you are going
to run your app on a case-sensitive filesystem.

To override an admin template for a specific app, copy and edit the template
from the ``django/contrib/admin/templates/admin`` directory, and save it to one
of the directories you just created.

For example, if we wanted to add a tool to the change list view for all the
models in an app named ``my_app``, we would copy
``contrib/admin/templates/admin/change_list.html`` to the
``templates/admin/my_app/`` directory of our project, and make any necessary
changes.

If we wanted to add a tool to the change list view for only a specific model
named 'Page', we would copy that same file to the
``templates/admin/my_app/page`` directory of our project.

Overriding vs. replacing an admin template
------------------------------------------

Because of the modular design of the admin templates, it is usually neither
necessary nor advisable to replace an entire template. It is almost always
better to override only the section of the template which you need to change.

To continue the example above, we want to add a new link next to the ``History``
tool for the ``Page`` model. After looking at ``change_form.html`` we determine
that we only need to override the ``object-tools`` block. Therefore here is our
new ``change_form.html`` :

.. code-block:: html+django

    {% extends "admin/change_form.html" %}
    {% load i18n %}
    {% block object-tools %}
    {% if change %}{% if not is_popup %}
      <ul class="object-tools">
        <li><a href="history/" class="historylink">{% trans "History" %}</a></li>
        <li><a href="mylink/" class="historylink">My Link</a></li>
        {% if has_absolute_url %}
            <li><a href="../../../r/{{ content_type_id }}/{{ object_id }}/" class="viewsitelink">
                {% trans "View on site" %}</a>
            </li>
        {% endif%}
      </ul>
    {% endif %}{% endif %}
    {% endblock %}

And that's it! If we placed this file in the ``templates/admin/my_app``
directory, our link would appear on every model's change form.

Templates which may be overridden per app or model
--------------------------------------------------

Not every template in ``contrib/admin/templates/admin`` may be overridden per
app or per model. The following can:

    * ``app_index.html``
    * ``change_form.html``
    * ``change_list.html``
    * ``delete_confirmation.html``
    * ``object_history.html``

For those templates that cannot be overridden in this way, you may still
override them for your entire project. Just place the new version in your
``templates/admin`` directory. This is particularly useful to create custom 404
and 500 pages.

.. note::

    Some of the admin templates, such as ``change_list_request.html`` are used
    to render custom inclusion tags. These may be overridden, but in such cases
    you are probably better off creating your own version of the tag in question
    and giving it a different name. That way you can use it selectively.

Root and login templates
------------------------

If you wish to change the index, login or logout templates, you are better off
creating your own ``AdminSite`` instance (see below), and changing the
:attr:`AdminSite.index_template` , :attr:`AdminSite.login_template` or
:attr:`AdminSite.logout_template` properties.

``AdminSite`` objects
=====================

.. class:: AdminSite(name=None)

A Django administrative site is represented by an instance of
``django.contrib.admin.sites.AdminSite``; by default, an instance of
this class is created as ``django.contrib.admin.site`` and you can
register your models and ``ModelAdmin`` instances with it.

If you'd like to set up your own administrative site with custom
behavior, however, you're free to subclass ``AdminSite`` and override
or add anything you like. Then, simply create an instance of your
``AdminSite`` subclass (the same way you'd instantiate any other
Python class), and register your models and ``ModelAdmin`` subclasses
with it instead of using the default.

.. versionadded:: 1.1

When constructing an instance of an ``AdminSite``, you are able to provide
a unique instance name using the ``name`` argument to the constructor. This
instance name is used to identify the instance, especially when
:ref:`reversing admin URLs <admin-reverse-urls>`. If no instance name is
provided, a default instance name of ``admin`` will be used.

``AdminSite`` attributes
------------------------

Templates can override or extend base admin templates as described in
`Overriding Admin Templates`_.

.. attribute:: AdminSite.index_template

Path to a custom template that will be used by the admin site main index view.

.. attribute:: AdminSite.login_template

Path to a custom template that will be used by the admin site login view.

.. attribute:: AdminSite.logout_template

.. versionadded:: 1.2

Path to a custom template that will be used by the admin site logout view.

.. attribute:: AdminSite.password_change_template

.. versionadded:: 1.2

Path to a custom template that will be used by the admin site password change
view.

.. attribute:: AdminSite.password_change_done_template

.. versionadded:: 1.2

Path to a custom template that will be used by the admin site password change
done view.

Hooking ``AdminSite`` instances into your URLconf
-------------------------------------------------

The last step in setting up the Django admin is to hook your ``AdminSite``
instance into your URLconf. Do this by pointing a given URL at the
``AdminSite.urls`` method.

In this example, we register the default ``AdminSite`` instance
``django.contrib.admin.site`` at the URL ``/admin/`` ::

    # urls.py
    from django.conf.urls.defaults import *
    from django.contrib import admin

    admin.autodiscover()

    urlpatterns = patterns('',
        (r'^admin/', include(admin.site.urls)),
    )

Above we used ``admin.autodiscover()`` to automatically load the
``INSTALLED_APPS`` admin.py modules.

In this example, we register the ``AdminSite`` instance
``myproject.admin.admin_site`` at the URL ``/myadmin/`` ::

    # urls.py
    from django.conf.urls.defaults import *
    from myproject.admin import admin_site

    urlpatterns = patterns('',
        (r'^myadmin/', include(admin_site.urls)),
    )

There is really no need to use autodiscover when using your own ``AdminSite``
instance since you will likely be importing all the per-app admin.py modules
in your ``myproject.admin`` module.

Multiple admin sites in the same URLconf
----------------------------------------

It's easy to create multiple instances of the admin site on the same
Django-powered Web site. Just create multiple instances of ``AdminSite`` and
root each one at a different URL.

.. versionchanged:: 1.1
    The method for hooking ``AdminSite`` instances into urls has changed in
    Django 1.1.

In this example, the URLs ``/basic-admin/`` and ``/advanced-admin/`` feature
separate versions of the admin site -- using the ``AdminSite`` instances
``myproject.admin.basic_site`` and ``myproject.admin.advanced_site``,
respectively::

    # urls.py
    from django.conf.urls.defaults import *
    from myproject.admin import basic_site, advanced_site

    urlpatterns = patterns('',
        (r'^basic-admin/', include(basic_site.urls)),
        (r'^advanced-admin/', include(advanced_site.urls)),
    )

``AdminSite`` instances take a single argument to their constructor, their
name, which can be anything you like. This argument becomes the prefix to the
URL names for the purposes of :ref:`reversing them<admin-reverse-urls>`. This
is only necessary if you are using more than one ``AdminSite``.

Adding views to admin sites
---------------------------

.. versionadded:: 1.1

Just like :class:`ModelAdmin`, :class:`AdminSite` provides a
:meth:`~django.contrib.admin.ModelAdmin.get_urls()` method
that can be overridden to define additional views for the site. To add
a new view to your admin site, extend the base
:meth:`~django.contrib.admin.ModelAdmin.get_urls()` method to include
a pattern for your new view.

.. note::
    Any view you render that uses the admin templates, or extends the base
    admin template, should provide the ``current_app`` argument to
    ``RequestContext`` or ``Context`` when rendering the template.  It should
    be set to either ``self.name`` if your view is on an ``AdminSite`` or
    ``self.admin_site.name`` if your view is on a ``ModelAdmin``.

.. _admin-reverse-urls:

Reversing Admin URLs
====================

.. versionadded:: 1.1

When an :class:`AdminSite` is deployed, the views provided by that site are
accessible using Django's :ref:`URL reversing system <naming-url-patterns>`.

The :class:`AdminSite` provides the following named URL patterns:

    ======================  ========================  =============
    Page                    URL name                  Parameters
    ======================  ========================  =============
    Index                   ``index``
    Logout                  ``logout``
    Password change         ``password_change``
    Password change done    ``password_change_done``
    i18n javascript         ``jsi18n``
    Application index page  ``app_list``              ``app_label``
    ======================  ========================  =============

Each :class:`ModelAdmin` instance provides an additional set of named URLs:

    ======================  ===============================================   =============
    Page                    URL name                                          Parameters
    ======================  ===============================================   =============
    Changelist              ``{{ app_label }}_{{ model_name }}_changelist``
    Add                     ``{{ app_label }}_{{ model_name }}_add``
    History                 ``{{ app_label }}_{{ model_name }}_history``      ``object_id``
    Delete                  ``{{ app_label }}_{{ model_name }}_delete``       ``object_id``
    Change                  ``{{ app_label }}_{{ model_name }}_change``       ``object_id``
    ======================  ===============================================   =============

These named URLs are registered with the application namespace ``admin``, and
with an instance namespace corresponding to the name of the Site instance.

So - if you wanted to get a reference to the Change view for a particular
``Choice`` object (from the polls application) in the default admin, you would
call::

    >>> from django.core import urlresolvers
    >>> c = Choice.objects.get(...)
    >>> change_url = urlresolvers.reverse('admin:polls_choice_change', args=(c.id,))

This will find the first registered instance of the admin application (whatever the instance
name), and resolve to the view for changing ``poll.Choice`` instances in that instance.

If you want to find a URL in a specific admin instance, provide the name of that instance
as a ``current_app`` hint to the reverse call. For example, if you specifically wanted
the admin view from the admin instance named ``custom``, you would need to call::

    >>> change_url = urlresolvers.reverse('custom:polls_choice_change', args=(c.id,))

For more details, see the documentation on :ref:`reversing namespaced URLs
<topics-http-reversing-url-namespaces>`.
