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Adrian Holovaty
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=====================================
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Writing your first Django app, part 2
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=====================================
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By Adrian Holovaty <holovaty@gmail.com>
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This tutorial begins where `Tutorial 1`_ left off. We're continuing the Web-poll
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application and will focus on Django's automatically-generated admin site.
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.. _Tutorial 1: http://www.djangoproject.com/documentation/tutorial1/
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Philosophy
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==========
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Generating admin sites for your staff or clients to add, change and delete
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content is tedious work that doesn't require much creativity. For that reason,
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Django entirely automates creation of admin interfaces for models.
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Django was written in a newsroom environment, with a very clear separation
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between "content publishers" and the "public" site. Site managers use the
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system to add news stories, events, sports scores, etc., and that content is
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displayed on the public site. Django solves the problem of creating a unified
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interface for site administrators to edit content.
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The admin isn't necessarily intended to be used by site visitors; it's for site
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managers.
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Expose the admin media files
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============================
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Django's admin is intended to be fully functional and good looking. For that
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reason, Django ships with admin media files -- CSS, JavaScript and images --
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that comprise the admin's design. To set up a Django admin instance, the first
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thing to do is put those media files online somewhere.
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(Note: Although Django ships with a default design for its admin site, you can
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change it however you'd like. The admin uses Django's own template system and
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is powered -- surprise, surprise -- by Django itself, so it is completely
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customizable.)
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The files are in the ``media`` directory of the Django distribution. To
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"activate" them, copy that directory under a Web document root somewhere, so
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that you can access them via the Web.
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Be careful not to put your Python source code under the Web document root. Just
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do the media files.
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Then, tell Django where you put them, via ``ADMIN_MEDIA_PREFIX`` in the
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``myproject.settings.admin`` settings file. Examples::
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# You can leave off the domain if they're on the same domain as your admin
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# site will be.
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ADMIN_MEDIA_PREFIX = '/adminmedia/'
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# Otherwise, use the fully-qualified domain.
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ADMIN_MEDIA_PREFIX = 'http://www.foo.com/adminmedia/'
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Make sure to include a trailing slash.
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Hook into mod_python
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====================
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Now let's take the opportunity to hook Django into Apache/mod_python. Edit your
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``httpd.conf`` file and add this::
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<Location "/admin/">
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SetHandler python-program
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PythonHandler django.core.handler
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SetEnv DJANGO_SETTINGS_MODULE myproject.settings.admin
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</Location>
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This tells Apache: "Use mod_python for any URL at or under '/admin/', using the
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Django mod_python handler." It also passes the value of ``DJANGO_SETTINGS_MODULE``,
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so mod_python knows which project to use. Note that we're passing the path to
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the ``admin`` settings, not the ``main`` settings. That's because this is the
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admin site, which has slightly different settings.
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You can also add directives such as ``PythonAutoReload Off`` for performance.
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See the `mod_python documentation`_ for a full list of options.
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When you've done that, restart Apache and go to /admin/ on your domain. You
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should see the admin's login screen:
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.. image:: http://media.djangoproject.com/img/doc/tutorial/admin01.png
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:alt: Django admin login screen
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.. _mod_python documentation: http://modpython.org/live/current/doc-html/directives.html
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Create a user account
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=====================
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We can't log in, though, because we haven't created an admin user account yet.
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Drop into the Python interactive interpreter and type this::
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# The function django.models.auth.users.create_user() creates a new user
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# and returns the new auth.User object.
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# Don't use 'username' and 'password'. Those are just examples.
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>>> from django.models.auth import users
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>>> u = users.create_user('username', 'your_email@domain.com', 'password')
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# But we're not done. We need to explicitly set is_staff and is_active to
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# allow this user to access the admin. Might as well make it a superuser,
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# too.
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u.is_staff = True
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u.is_active = True
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u.is_superuser = True
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# Remember, call the save() method to save changes.
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u.save()
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Enter the admin site
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====================
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Now, try logging in. If the login worked, you should see the Django admin index
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page:
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.. image:: http://media.djangoproject.com/img/doc/tutorial/admin02t.png
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:alt: Django admin index page
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:target: http://media.djangoproject.com/img/doc/tutorial/admin02.png
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By default, you should see four types of editable content: groups, users,
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redirects and flat files. These are core features Django ships with by default.
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Make the poll app modifiable in the admin
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=========================================
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But where's our poll app? It's not displayed on the admin index page.
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Just one thing to do: We need to specify in the ``polls.Poll`` model that Poll
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objects have an admin interface. Edit the ``myproject/apps/polls/models/polls.py``
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file and make the following change to add an ``admin`` attribute::
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class Poll(meta.Model):
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fields = (
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# ...
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)
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admin = meta.Admin(
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fields = (
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(None, {'fields': ('question', 'pub_date')}),
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),
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)
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Reload the Django admin index page. Note that you might have to restart Apache,
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depending on your Apache settings. Because mod_python saves code in memory for
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performance, Python code changes generally aren't reflected until Apache
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restarts. One way around this is to set ``MaxRequestsPerChild 1`` in your
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httpd.conf to force Apache to reload everything for each request. But don't do
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that on a production server, or we'll revoke your Django privileges.
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Explore the free admin functionality
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====================================
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Now that ``Poll`` has the ``admin`` attribute, Django knows that it should be
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displayed on the admin index page:
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.. image:: http://media.djangoproject.com/img/doc/tutorial/admin03t.png
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:alt: Django admin index page, now with polls displayed
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:target: http://media.djangoproject.com/img/doc/tutorial/admin03.png
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Click "Polls." Now you're at the "change list" page for polls. This page
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displays all the polls in the database and lets you choose one to change it.
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There's the "What's up?" poll we created in the first tutorial:
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.. image:: http://media.djangoproject.com/img/doc/tutorial/admin04t.png
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:alt: Polls change list page
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:target: http://media.djangoproject.com/img/doc/tutorial/admin04.png
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Click the "What's up?" poll to edit it:
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.. image:: http://media.djangoproject.com/img/doc/tutorial/admin05t.png
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:alt: Editing form for poll object
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:target: http://media.djangoproject.com/img/doc/tutorial/admin05.png
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Things to note here:
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* The form is automatically generated from the Poll model.
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* The different model field types (``meta.DateTimeField``, ``meta.CharField``)
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correspond to the appropriate HTML input widget. Each type of field knows
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how to display itself in the Django admin.
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* ``DateTimeField``s get free JavaScript shortcuts. Dates get a "Today"
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shortcut and calendar popup, and times get a "Now" shortcut and a convenient
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popup that lists commonly entered times.
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* The bottom part of the page gives you a couple of options:
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* Save -- Saves changes and returns to the changelist page for this type of
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object.
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* Save and continue editing -- Saves changes and reloads the admin page for
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this object.
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* Save and add another -- Saves changes and loads a new, blank form for this
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type of object.
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* Delete -- Displays a delete confirmation page.
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Change the "Date published" by clicking the "Today" and "Now" shortcuts. Then
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click "Save and continue editing." Then click "History" in the upper right.
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You'll see a page listing all changes made to this object via the Django admin,
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with the timestamp and username of the person who made the change:
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.. image:: http://media.djangoproject.com/img/doc/tutorial/admin06t.png
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:alt: History page for poll object
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:target: http://media.djangoproject.com/img/doc/tutorial/admin06.png
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Customize the admin form
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========================
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Take a few minutes to marvel at all the code you didn't have to write.
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Let's customize this a bit. We can reorder the fields by changing the
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order of the field names in the ``admin`` attribute of the model::
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admin = meta.Admin(
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fields = (
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(None, {'fields': ('pub_date', 'question')}),
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),
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)
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That made the "Publication date" show up first instead of second:
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.. image:: http://media.djangoproject.com/img/doc/tutorial/admin07.png
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:alt: Fields have been reordered
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This isn't impressive with only two fields, but for admin forms with dozens
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of fields, choosing an intuitive order is an important usability detail.
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And speaking of forms with dozens of fields, you might want to split the form
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up into fieldsets::
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admin = meta.Admin(
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fields = (
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(None, {'fields': ('question',)}),
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('Date information', {'fields': ('pub_date',)}),
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),
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)
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The first element of each tuple in ``fields`` is the title of the fieldset.
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Here's what our form looks like now:
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.. image:: http://media.djangoproject.com/img/doc/tutorial/admin08t.png
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:alt: Form has fieldsets now
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:target: http://media.djangoproject.com/img/doc/tutorial/admin08.png
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You can assign arbitrary HTML classes to each fieldset. Django provides a
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``"collapse"`` class that displays a particular fieldset initially collapsed.
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This is useful when you have a long form that contains a number of fields that
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aren't commonly used::
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admin = meta.Admin(
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fields = (
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(None, {'fields': ('question',)}),
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('Date information', {'fields': ('pub_date',), 'classes': 'collapse'}),
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),
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)
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.. image:: http://media.djangoproject.com/img/doc/tutorial/admin09.png
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:alt: Fieldset is initially collapsed
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Customize the admin change list
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===============================
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There's much more to come. This document is not finished.
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