===================================== 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/ 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. Expose the admin media files ============================ Django's admin is intended to be fully functional and good looking. For that reason, Django ships with admin media files -- CSS, JavaScript and images -- that comprise the admin's design. To set up a Django admin instance, the first thing to do is put those media files online somewhere. (Note: Although Django ships with a default design for its admin site, you can change it however you'd like. The admin uses Django's own template system and is powered -- surprise, surprise -- by Django itself, so it is completely customizable.) The files are in the ``media`` directory of the Django distribution. To "activate" them, copy that directory under a Web document root somewhere, so that you can access them via the Web. Be careful not to put your Python source code under the Web document root. Just do the media files. Then, tell Django where you put them, via ``ADMIN_MEDIA_PREFIX`` in the ``myproject.settings.admin`` settings file. Examples:: # You can leave off the domain if they're on the same domain as your admin # site will be. ADMIN_MEDIA_PREFIX = '/adminmedia/' # Otherwise, use the fully-qualified domain. ADMIN_MEDIA_PREFIX = 'http://www.foo.com/adminmedia/' Make sure to include a trailing slash. Hook into mod_python ==================== Now let's take the opportunity to hook Django into Apache/mod_python. Edit your ``httpd.conf`` file and add this:: SetHandler python-program PythonHandler django.core.handler SetEnv DJANGO_SETTINGS_MODULE myproject.settings.admin This tells Apache: "Use mod_python for any URL at or under '/admin/', using the Django mod_python handler." It also passes the value of ``DJANGO_SETTINGS_MODULE``, so mod_python knows which project to use. Note that we're passing the path to the ``admin`` settings, not the ``main`` settings. That's because this is the admin site, which has slightly different settings. You can also add directives such as ``PythonAutoReload Off`` for performance. See the `mod_python documentation`_ for a full list of options. When you've done that, restart Apache and go to /admin/ on your domain. You should see the admin's login screen: .. image:: http://media.djangoproject.com/img/doc/tutorial/admin01.png :alt: Django admin login screen .. _mod_python documentation: http://modpython.org/live/current/doc-html/directives.html Create a user account ===================== We can't log in, though, because we haven't created an admin user account yet. Drop into the Python interactive interpreter and type this:: # The function django.models.auth.users.create_user() creates a new user # and returns the new auth.User object. # Don't use 'username' and 'password'. Those are just examples. >>> from django.models.auth import users >>> u = users.create_user('username', 'your_email@domain.com', 'password') # But we're not done. We need to explicitly set is_staff and is_active to # allow this user to access the admin. Might as well make it a superuser, # too. u.is_staff = True u.is_active = True u.is_superuser = True # Remember, call the save() method to save changes. u.save() Enter the admin site ==================== Now, try logging in. If it didn't work, read the `"I can't log in" questions`_ in the FAQ. If it worked, 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 four types of editable content: groups, users, redirects and flat files. 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 ``admin`` attribute:: class Poll(meta.Model): fields = ( # ... ) admin = meta.Admin( fields = ( (None, {'fields': ('question', 'pub_date')}), ), ) Reload the Django admin index page. Note that you might have to restart Apache, depending on your Apache settings. Because mod_python saves code in memory for performance, Python code changes generally aren't reflected until Apache restarts. One way around this is to set ``MaxRequestsPerChild 1`` in your httpd.conf to force Apache to reload everything for each request. But don't do that on a production server, or we'll revoke your Django privileges. 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 changing the order of the field names in the ``admin`` attribute of the model:: 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): # ... admin = meta.Admin( fields = ( (None, {'fields': ('poll_id', 'choice', 'votes')}), ), ) (Note that we used "poll_id" to refer to the ``ForeignKey(Poll)`` field. The field name is automatically calculated from the model's class name, lowercased, plus '_id'.) 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:: meta.ForeignKey(Poll, edit_inline=True, 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``:: meta.CharField('choice', 'choice', maxlength=200, core=True), meta.IntegerField('votes', 'votes', 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 at least one 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:: meta.ForeignKey(Poll, edit_inline=True, num_in_admin=3, edit_inline_type=meta.TABULAR), With that ``edit_inline_type=meta.TABULAR``, 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 More ==== There's much more to come. This document is not finished.