===================================== Writing your first Django app, part 2 ===================================== By Adrian Holovaty This tutorial begins where `Tutorial 1`_ left off. We're continuing the Web-poll application and will focus on Django's automatically-generated admin site. .. _Tutorial 1: http://www.djangoproject.com/documentation/tutorial1/ .. admonition:: Philosophy Generating admin sites for your staff or clients to add, change and delete content is tedious work that doesn't require much creativity. For that reason, Django entirely automates creation of admin interfaces for models. Django was written in a newsroom environment, with a very clear separation between "content publishers" and the "public" site. Site managers use the system to add news stories, events, sports scores, etc., and that content is displayed on the public site. Django solves the problem of creating a unified interface for site administrators to edit content. The admin isn't necessarily intended to be used by site visitors; it's for site managers. Activate the admin site ======================= The Django admin site is not activated by default -- it's an opt-in thing. To activate the admin site for your installation, do these three things: * Add ``"django.contrib.admin"`` to your ``INSTALLED_APPS`` setting. * Run the command ``django-admin.py install admin``. This will create an extra database table that the admin needs. * Edit your ``myproject.urls`` file and uncomment the line below "Uncomment this for admin:". This file is a URLconf; we'll dig into URLconfs in the next tutorial. For now, all you need to know is that it maps URL roots to applications. Create a user account ===================== Run the following command to create a superuser account for your admin site:: django-admin.py createsuperuser --settings=myproject.settings The script will prompt you for a username, e-mail address and password (twice). Start the development server ============================ To make things easy, Django comes with a pure-Python Web server that builds on the BaseHTTPServer included in Python's standard library. Let's start the server and explore the admin site. Just run the following command to start the server:: django-admin.py runserver --settings=myproject.settings It'll start a Web server running locally -- on port 8000, by default. If you want to change the server's port, pass it as a command-line argument:: django-admin.py runserver 8080 --settings=myproject.settings DON'T use this server in anything resembling a production environment. It's intended only for use while developing. Now, open a Web browser and go to "/admin/" on your local domain -- e.g., http://127.0.0.1:8000/admin/. You should see the admin's login screen: .. image:: http://media.djangoproject.com/img/doc/tutorial/admin01.png :alt: Django admin login screen Enter the admin site ==================== Now, try logging in. You should see the Django admin index page: .. image:: http://media.djangoproject.com/img/doc/tutorial/admin02t.png :alt: Django admin index page :target: http://media.djangoproject.com/img/doc/tutorial/admin02.png By default, you should see two types of editable content: groups and users. These are core features Django ships with by default. .. _"I can't log in" questions: http://www.djangoproject.com/documentation/faq/#the-admin-site Make the poll app modifiable in the admin ========================================= But where's our poll app? It's not displayed on the admin index page. Just one thing to do: We need to specify in the ``polls.Poll`` model that Poll objects have an admin interface. Edit the ``myproject/apps/polls/models/polls.py`` file and make the following change to add an inner ``META`` class with an ``admin`` attribute:: class Poll(meta.Model): # ... class META: admin = meta.Admin() The ``class META`` contains all non-field metadata about this model. Now reload the Django admin page to see your changes. Note that you don't have to restart the development server -- it auto-reloads code. Explore the free admin functionality ==================================== Now that ``Poll`` has the ``admin`` attribute, Django knows that it should be displayed on the admin index page: .. image:: http://media.djangoproject.com/img/doc/tutorial/admin03t.png :alt: Django admin index page, now with polls displayed :target: http://media.djangoproject.com/img/doc/tutorial/admin03.png Click "Polls." Now you're at the "change list" page for polls. This page displays all the polls in the database and lets you choose one to change it. There's the "What's up?" poll we created in the first tutorial: .. image:: http://media.djangoproject.com/img/doc/tutorial/admin04t.png :alt: Polls change list page :target: http://media.djangoproject.com/img/doc/tutorial/admin04.png Click the "What's up?" poll to edit it: .. image:: http://media.djangoproject.com/img/doc/tutorial/admin05t.png :alt: Editing form for poll object :target: http://media.djangoproject.com/img/doc/tutorial/admin05.png Things to note here: * The form is automatically generated from the Poll model. * The different model field types (``meta.DateTimeField``, ``meta.CharField``) correspond to the appropriate HTML input widget. Each type of field knows how to display itself in the Django admin. * Each ``DateTimeField`` gets free JavaScript shortcuts. Dates get a "Today" shortcut and calendar popup, and times get a "Now" shortcut and a convenient popup that lists commonly entered times. The bottom part of the page gives you a couple of options: * Save -- Saves changes and returns to the change-list page for this type of object. * Save and continue editing -- Saves changes and reloads the admin page for this object. * Save and add another -- Saves changes and loads a new, blank form for this type of object. * Delete -- Displays a delete confirmation page. Change the "Date published" by clicking the "Today" and "Now" shortcuts. Then click "Save and continue editing." Then click "History" in the upper right. You'll see a page listing all changes made to this object via the Django admin, with the timestamp and username of the person who made the change: .. image:: http://media.djangoproject.com/img/doc/tutorial/admin06t.png :alt: History page for poll object :target: http://media.djangoproject.com/img/doc/tutorial/admin06.png Customize the admin form ======================== Take a few minutes to marvel at all the code you didn't have to write. Let's customize this a bit. We can reorder the fields by explicitly adding a ``fields`` parameter to ``meta.Admin``:: admin = meta.Admin( fields = ( (None, {'fields': ('pub_date', 'question')}), ), ) That made the "Publication date" show up first instead of second: .. image:: http://media.djangoproject.com/img/doc/tutorial/admin07.png :alt: Fields have been reordered This isn't impressive with only two fields, but for admin forms with dozens of fields, choosing an intuitive order is an important usability detail. And speaking of forms with dozens of fields, you might want to split the form up into fieldsets:: admin = meta.Admin( fields = ( (None, {'fields': ('question',)}), ('Date information', {'fields': ('pub_date',)}), ), ) The first element of each tuple in ``fields`` is the title of the fieldset. Here's what our form looks like now: .. image:: http://media.djangoproject.com/img/doc/tutorial/admin08t.png :alt: Form has fieldsets now :target: http://media.djangoproject.com/img/doc/tutorial/admin08.png You can assign arbitrary HTML classes to each fieldset. Django provides a ``"collapse"`` class that displays a particular fieldset initially collapsed. This is useful when you have a long form that contains a number of fields that aren't commonly used:: admin = meta.Admin( fields = ( (None, {'fields': ('question',)}), ('Date information', {'fields': ('pub_date',), 'classes': 'collapse'}), ), ) .. image:: http://media.djangoproject.com/img/doc/tutorial/admin09.png :alt: Fieldset is initially collapsed Adding related objects ====================== OK, we have our Poll admin page. But a ``Poll`` has multiple ``Choices``, and the admin page doesn't display choices. Yet. In this case, there are two ways to solve this problem. The first is to give the ``Choice`` model its own ``admin`` attribute, just as we did with ``Poll``. Here's what that would look like:: class Choice(meta.Model): # ... class META: admin = meta.Admin() Now "Choices" is an available option in the Django admin. The "Add choice" form looks like this: .. image:: http://media.djangoproject.com/img/doc/tutorial/admin10.png :alt: Choice admin page In that form, the "Poll" field is a select box containing every poll in the database. In our case, only one poll exists at this point. Also note the "Add Another" link next to "Poll." Every object with a ForeignKey relationship to another gets this for free. When you click "Add Another," you'll get a popup window with the "Add poll" form. If you add a poll in that window and click "Save," Django will save the poll to the database and dynamically add it as the selected choice on the "Add choice" form you're looking at. But, really, this is an inefficient way of adding Choice objects to the system. It'd be better if you could add a bunch of Choices directly when you create the Poll object. Let's make that happen. Remove the ``admin`` for the Choice model. Then, edit the ``ForeignKey(Poll)`` field like so:: poll = meta.ForeignKey(Poll, edit_inline=meta.STACKED, num_in_admin=3) This tells Django: "Choice objects are edited on the Poll admin page. By default, provide enough fields for 3 Choices." Then change the other fields in ``Choice`` to give them ``core=True``:: choice = meta.CharField(maxlength=200, core=True) votes = meta.IntegerField(core=True) This tells Django: "When you edit a Choice on the Poll admin page, the 'choice' and 'votes' fields are required. The presence of at least one of them signifies the addition of a new Choice object, and clearing both of them signifies the deletion of that existing Choice object." Load the "Add poll" page to see how that looks: .. image:: http://media.djangoproject.com/img/doc/tutorial/admin11t.png :alt: Add poll page now has choices on it :target: http://media.djangoproject.com/img/doc/tutorial/admin11.png It works like this: There are three slots for related Choices -- as specified by ``num_in_admin`` -- but each time you come back to the "Change" page for an already-created object, you get one extra slot. (This means there's no hard-coded limit on how many related objects can be added.) If you wanted space for three extra Choices each time you changed the poll, you'd use ``num_extra_on_change=3``. One small problem, though. It takes a lot of screen space to display all the fields for entering related Choice objects. For that reason, Django offers an alternate way of displaying inline related objects:: poll = meta.ForeignKey(Poll, edit_inline=meta.TABULAR, num_in_admin=3) With that ``edit_inline=meta.TABULAR`` (instead of ``meta.STACKED``), the related objects are displayed in a more compact, table-based format: .. image:: http://media.djangoproject.com/img/doc/tutorial/admin12.png :alt: Add poll page now has more compact choices Customize the admin change list =============================== Now that the Poll admin page is looking good, let's make some tweaks to the "change list" page -- the one that displays all the polls in the system. Here's what it looks like at this point: .. image:: http://media.djangoproject.com/img/doc/tutorial/admin04t.png :alt: Polls change list page :target: http://media.djangoproject.com/img/doc/tutorial/admin04.png By default, Django displays the ``repr()`` of each object. But it'd be more helpful if we could display individual fields. To do that, use the ``list_display`` option, which is a tuple of field names to display, as columns, on the change list page for the object:: class Poll(meta.Model): # ... class META: admin = meta.Admin( # ... list_display = ('question', 'pub_date'), ) Just for good measure, let's also include the ``was_published_today`` custom method from Tutorial 1:: list_display = ('question', 'pub_date', 'was_published_today'), Now the poll change list page looks like this: .. image:: http://media.djangoproject.com/img/doc/tutorial/admin13t.png :alt: Polls change list page, updated :target: http://media.djangoproject.com/img/doc/tutorial/admin13.png You can click on the column headers to sort by those values -- except in the case of the ``was_published_today`` header, because sorting by the output of an arbitrary method is not supported. Also note that the column header for ``was_published_today`` is, by default, the name of the method (with underscores replaced with spaces). But you can change that by giving that method a ``short_description`` attribute:: def was_published_today(self): return self.pub_date.date() == datetime.date.today() was_published_today.short_description = 'Published today?' Let's add another improvement to the Poll change list page: Filters. Add the following line to ``Poll.admin``:: list_filter = ['pub_date'], That adds a "Filter" sidebar that lets people filter the change list by the ``pub_date`` field: .. image:: http://media.djangoproject.com/img/doc/tutorial/admin14t.png :alt: Polls change list page, updated :target: http://media.djangoproject.com/img/doc/tutorial/admin14.png The type of filter displayed depends on the type of field you're filtering on. Because ``pub_date`` is a DateTimeField, Django knows to give the default filter options for DateTimeFields: "Any date," "Today," "Past 7 days," "This month," "This year." This is shaping up well. Let's add some search capability:: search_fields = ['question'], That adds a search box at the top of the change list. When somebody enters search terms, Django will search the ``question`` field. You can use as many fields as you'd like -- although because it uses a LIKE query behind the scenes, keep it reasonable, to keep your database happy. Finally, because Poll objects have dates, it'd be convenient to be able to drill down by date. Add this line:: date_hierarchy = 'pub_date', That adds hierarchical navigation, by date, to the top of the change list page. At top level, it displays all available years. Then it drills down to months and, ultimately, days. Now's also a good time to note that change lists give you free pagination. The default is to display 50 items per page. Change-list pagination, search boxes, filters, date-hierarchies and column-header-ordering all work together like you think they should. Customize the admin look and feel ================================= Clearly, having "Django administration" and "example.com" at the top of each admin page is ridiculous. It's just placeholder text. That's easy to change, though, using Django's template system. The Django admin is powered by Django itself, and its interfaces use Django's own template system. (How meta!) Open your settings file (``myproject/settings.py``, remember) and look at the ``TEMPLATE_DIRS`` setting. ``TEMPLATE_DIRS`` is a tuple of filesystem directories to check when loading Django templates. It's a search path. By default, ``TEMPLATE_DIRS`` is empty. So, let's add a line to it, to tell Django where our templates live:: TEMPLATE_DIRS = ( "/home/mytemplates", # Change this to your own directory. ) Now copy the template ``admin/base_site.html`` from within the default Django admin template directory (``django/contrib/admin/templates``) into an ``admin`` subdirectory of whichever directory you're using in ``TEMPLATE_DIRS``. For example, if your ``TEMPLATE_DIRS`` includes ``"/home/mytemplates"``, as above, then copy ``django/contrib/admin/templates/admin/base_site.html`` to ``/home/mytemplates/admin/base_site.html``. Then, just edit the file and replace the generic Django text with your own site's name and URL as you see fit. Note that any of Django's default admin templates can be overridden. To override a template, just do the same thing you did with ``base_site.html`` -- copy it from the default directory into your custom directory, and make changes. Astute readers will ask: But if ``TEMPLATE_DIRS`` was empty by default, how was Django finding the default admin templates? The answer is that, by default, Django automatically looks for a ``templates/`` subdirectory within each app package, for use as a fallback. See the `loader types documentation`_ for full information. .. _loader types documentation: http://www.djangoproject.com/documentation/templates_python/#loader-types Customize the admin index page ============================== On a similar note, you might want to customize the look and feel of the Django admin index page. By default, it displays all available apps, according to your ``INSTALLED_APPS`` setting. But the order in which it displays things is random, and you may want to make significant changes to the layout. After all, the index is probably the most important page of the admin, and it should be easy to use. The template to customize is ``admin/index.html``. (Do the same as with ``admin/base_site.html`` in the previous section -- copy it from the default directory to your custom template directory.) Edit the file, and you'll see it uses a template tag called ``{% get_admin_app_list as app_list %}``. That's the magic that retrieves every installed Django app. Instead of using that, you can hard-code links to object-specific admin pages in whatever way you think is best. Django offers another shortcut in this department. Run the command ``django-admin.py adminindex polls`` to get a chunk of template code for inclusion in the admin index template. It's a useful starting point. For full details on customizing the look and feel of the Django admin site in general, see the `Django admin CSS guide`_. When you're comfortable with the admin site, read `part 3 of this tutorial`_ to start working on public poll views. .. _Django admin CSS guide: http://www.djangoproject.com/documentation/admin_css/ .. _part 3 of this tutorial: http://www.djangoproject.com/documentation/tutorial3/