1 =====================================

     2 Writing your first Django app, part 2

     3 =====================================

     4 

     5 This tutorial begins where `Tutorial 1`_ left off. We're continuing the Web-poll

     6 application and will focus on Django's automatically-generated admin site.

     7 

     8 .. _Tutorial 1: ../tutorial1/

     9 

    10 .. admonition:: Philosophy

    11 

    12     Generating admin sites for your staff or clients to add, change and delete

    13     content is tedious work that doesn't require much creativity. For that reason,

    14     Django entirely automates creation of admin interfaces for models.

    15 

    16     Django was written in a newsroom environment, with a very clear separation

    17     between "content publishers" and the "public" site. Site managers use the

    18     system to add news stories, events, sports scores, etc., and that content is

    19     displayed on the public site. Django solves the problem of creating a unified

    20     interface for site administrators to edit content.

    21 

    22     The admin isn't necessarily intended to be used by site visitors; it's for site

    23     managers.

    24 

    25 Activate the admin site

    26 =======================

    27 

    28 The Django admin site is not activated by default -- it's an opt-in thing. To

    29 activate the admin site for your installation, do these three things:

    30 

    31     * Add ``"django.contrib.admin"`` to your ``INSTALLED_APPS`` setting.

    32     * Run ``python manage.py syncdb``. Since you have added a new application

    33       to ``INSTALLED_APPS``, the database tables need to be updated.

    34     * Edit your ``mysite/urls.py`` file and uncomment the line below

    35       "Uncomment this for admin:". This file is a URLconf; we'll dig into

    36       URLconfs in the next tutorial. For now, all you need to know is that it

    37       maps URL roots to applications.

    38 

    39 Start the development server

    40 ============================

    41 

    42 Let's start the development server and explore the admin site.

    43 

    44 Recall from Tutorial 1 that you start the development server like so::

    45 

    46     python manage.py runserver

    47 

    48 Now, open a Web browser and go to "/admin/" on your local domain -- e.g.,

    49 http://127.0.0.1:8000/admin/. You should see the admin's login screen:

    50 

    51 .. image:: http://media.djangoproject.com/img/doc/tutorial/admin01.png

    52    :alt: Django admin login screen

    53 

    54 Enter the admin site

    55 ====================

    56 

    57 Now, try logging in. (You created a superuser account in the first part of this

    58 tutorial, remember?) You should see the Django admin index page:

    59 

    60 .. image:: http://media.djangoproject.com/img/doc/tutorial/admin02t.png

    61    :alt: Django admin index page

    62    :target: http://media.djangoproject.com/img/doc/tutorial/admin02.png

    63 

    64 By default, you should see two types of editable content: groups and users.

    65 These are core features Django ships with by default.

    66 

    67 .. _"I can't log in" questions: ../faq/#the-admin-site

    68 

    69 Make the poll app modifiable in the admin

    70 =========================================

    71 

    72 But where's our poll app? It's not displayed on the admin index page.

    73 

    74 Just one thing to do: We need to specify in the ``Poll`` model that ``Poll``

    75 objects have an admin interface. Edit the ``mysite/polls/models.py`` file and

    76 make the following change to add an inner ``Admin`` class::

    77 

    78     class Poll(models.Model):

    79         # ...

    80         class Admin:

    81             pass

    82 

    83 The ``class Admin`` will contain all the settings that control how this model

    84 appears in the Django admin.  All the settings are optional, however, so

    85 creating an empty class means "give this object an admin interface using

    86 all the default options."

    87 

    88 Now reload the Django admin page to see your changes. Note that you don't have

    89 to restart the development server -- the server will auto-reload your project,

    90 so any modifications code will be seen immediately in your browser.

    91 

    92 Explore the free admin functionality

    93 ====================================

    94 

    95 Now that ``Poll`` has the inner ``Admin`` class, Django knows that it should be

    96 displayed on the admin index page:

    97 

    98 .. image:: http://media.djangoproject.com/img/doc/tutorial/admin03t.png

    99    :alt: Django admin index page, now with polls displayed

   100    :target: http://media.djangoproject.com/img/doc/tutorial/admin03.png

   101 

   102 Click "Polls." Now you're at the "change list" page for polls. This page

   103 displays all the polls in the database and lets you choose one to change it.

   104 There's the "What's up?" poll we created in the first tutorial:

   105 

   106 .. image:: http://media.djangoproject.com/img/doc/tutorial/admin04t.png

   107    :alt: Polls change list page

   108    :target: http://media.djangoproject.com/img/doc/tutorial/admin04.png

   109 

   110 Click the "What's up?" poll to edit it:

   111 

   112 .. image:: http://media.djangoproject.com/img/doc/tutorial/admin05t.png

   113    :alt: Editing form for poll object

   114    :target: http://media.djangoproject.com/img/doc/tutorial/admin05.png

   115 

   116 Things to note here:

   117 

   118 * The form is automatically generated from the Poll model.

   119 * The different model field types (``models.DateTimeField``, ``models.CharField``)

   120   correspond to the appropriate HTML input widget. Each type of field knows

   121   how to display itself in the Django admin.

   122 * Each ``DateTimeField`` gets free JavaScript shortcuts. Dates get a "Today"

   123   shortcut and calendar popup, and times get a "Now" shortcut and a convenient

   124   popup that lists commonly entered times.

   125 

   126 The bottom part of the page gives you a couple of options:

   127 

   128 * Save -- Saves changes and returns to the change-list page for this type of

   129   object.

   130 * Save and continue editing -- Saves changes and reloads the admin page for

   131   this object.

   132 * Save and add another -- Saves changes and loads a new, blank form for this

   133   type of object.

   134 * Delete -- Displays a delete confirmation page.

   135 

   136 Change the "Date published" by clicking the "Today" and "Now" shortcuts. Then

   137 click "Save and continue editing." Then click "History" in the upper right.

   138 You'll see a page listing all changes made to this object via the Django admin,

   139 with the timestamp and username of the person who made the change:

   140 

   141 .. image:: http://media.djangoproject.com/img/doc/tutorial/admin06t.png

   142    :alt: History page for poll object

   143    :target: http://media.djangoproject.com/img/doc/tutorial/admin06.png

   144 

   145 Customize the admin form

   146 ========================

   147 

   148 Take a few minutes to marvel at all the code you didn't have to write.

   149 

   150 Let's customize this a bit. We can reorder the fields by explicitly adding a

   151 ``fields`` parameter to ``Admin``::

   152 

   153         class Admin:

   154             fields = (

   155                 (None, {'fields': ('pub_date', 'question')}),

   156             )

   157 

   158 That made the "Publication date" show up first instead of second:

   159 

   160 .. image:: http://media.djangoproject.com/img/doc/tutorial/admin07.png

   161    :alt: Fields have been reordered

   162 

   163 This isn't impressive with only two fields, but for admin forms with dozens

   164 of fields, choosing an intuitive order is an important usability detail.

   165 

   166 And speaking of forms with dozens of fields, you might want to split the form

   167 up into fieldsets::

   168 

   169         class Admin:

   170             fields = (

   171                 (None, {'fields': ('question',)}),

   172                 ('Date information', {'fields': ('pub_date',)}),

   173             )

   174 

   175 The first element of each tuple in ``fields`` is the title of the fieldset.

   176 Here's what our form looks like now:

   177 

   178 .. image:: http://media.djangoproject.com/img/doc/tutorial/admin08t.png

   179    :alt: Form has fieldsets now

   180    :target: http://media.djangoproject.com/img/doc/tutorial/admin08.png

   181 

   182 You can assign arbitrary HTML classes to each fieldset. Django provides a

   183 ``"collapse"`` class that displays a particular fieldset initially collapsed.

   184 This is useful when you have a long form that contains a number of fields that

   185 aren't commonly used::

   186 

   187         class Admin:

   188             fields = (

   189                 (None, {'fields': ('question',)}),

   190                 ('Date information', {'fields': ('pub_date',), 'classes': 'collapse'}),

   191             )

   192 

   193 .. image:: http://media.djangoproject.com/img/doc/tutorial/admin09.png

   194    :alt: Fieldset is initially collapsed

   195 

   196 Adding related objects

   197 ======================

   198 

   199 OK, we have our Poll admin page. But a ``Poll`` has multiple ``Choices``, and

   200 the admin page doesn't display choices.

   201 

   202 Yet.

   203 

   204 There are two ways to solve this problem. The first is to give the ``Choice``

   205 model its own inner ``Admin`` class, just as we did with ``Poll``. Here's what

   206 that would look like::

   207 

   208     class Choice(models.Model):

   209         # ...

   210         class Admin:

   211             pass

   212 

   213 Now "Choices" is an available option in the Django admin. The "Add choice" form

   214 looks like this:

   215 

   216 .. image:: http://media.djangoproject.com/img/doc/tutorial/admin10.png

   217    :alt: Choice admin page

   218 

   219 In that form, the "Poll" field is a select box containing every poll in the

   220 database. Django knows that a ``ForeignKey`` should be represented in the admin

   221 as a ``<select>`` box. In our case, only one poll exists at this point.

   222 

   223 Also note the "Add Another" link next to "Poll." Every object with a ForeignKey

   224 relationship to another gets this for free. When you click "Add Another," you'll

   225 get a popup window with the "Add poll" form. If you add a poll in that window

   226 and click "Save," Django will save the poll to the database and dynamically add

   227 it as the selected choice on the "Add choice" form you're looking at.

   228 

   229 But, really, this is an inefficient way of adding Choice objects to the system.

   230 It'd be better if you could add a bunch of Choices directly when you create the

   231 Poll object. Let's make that happen.

   232 

   233 Remove the ``Admin`` for the Choice model. Then, edit the ``ForeignKey(Poll)``

   234 field like so::

   235 

   236     poll = models.ForeignKey(Poll, edit_inline=models.STACKED, num_in_admin=3)

   237 

   238 This tells Django: "Choice objects are edited on the Poll admin page. By

   239 default, provide enough fields for 3 Choices."

   240 

   241 Then change the other fields in ``Choice`` to give them ``core=True``::

   242 

   243     choice = models.CharField(maxlength=200, core=True)

   244     votes = models.IntegerField(core=True)

   245 

   246 This tells Django: "When you edit a Choice on the Poll admin page, the 'choice'

   247 and 'votes' fields are required. The presence of at least one of them signifies

   248 the addition of a new Choice object, and clearing both of them signifies the

   249 deletion of that existing Choice object."

   250 

   251 Load the "Add poll" page to see how that looks:

   252 

   253 .. image:: http://media.djangoproject.com/img/doc/tutorial/admin11t.png

   254    :alt: Add poll page now has choices on it

   255    :target: http://media.djangoproject.com/img/doc/tutorial/admin11.png

   256 

   257 It works like this: There are three slots for related Choices -- as specified

   258 by ``num_in_admin`` -- but each time you come back to the "Change" page for an

   259 already-created object, you get one extra slot. (This means there's no

   260 hard-coded limit on how many related objects can be added.) If you wanted space

   261 for three extra Choices each time you changed the poll, you'd use

   262 ``num_extra_on_change=3``.

   263 

   264 One small problem, though. It takes a lot of screen space to display all the

   265 fields for entering related Choice objects. For that reason, Django offers an

   266 alternate way of displaying inline related objects::

   267 

   268     poll = models.ForeignKey(Poll, edit_inline=models.TABULAR, num_in_admin=3)

   269 

   270 With that ``edit_inline=models.TABULAR`` (instead of ``models.STACKED``), the

   271 related objects are displayed in a more compact, table-based format:

   272 

   273 .. image:: http://media.djangoproject.com/img/doc/tutorial/admin12.png

   274    :alt: Add poll page now has more compact choices

   275 

   276 Customize the admin change list

   277 ===============================

   278 

   279 Now that the Poll admin page is looking good, let's make some tweaks to the

   280 "change list" page -- the one that displays all the polls in the system.

   281 

   282 Here's what it looks like at this point:

   283 

   284 .. image:: http://media.djangoproject.com/img/doc/tutorial/admin04t.png

   285    :alt: Polls change list page

   286    :target: http://media.djangoproject.com/img/doc/tutorial/admin04.png

   287 

   288 By default, Django displays the ``str()`` of each object. But sometimes it'd

   289 be more helpful if we could display individual fields. To do that, use the

   290 ``list_display`` option, which is a tuple of field names to display, as columns,

   291 on the change list page for the object::

   292 

   293     class Poll(models.Model):

   294         # ...

   295         class Admin:

   296             # ...

   297             list_display = ('question', 'pub_date')

   298 

   299 Just for good measure, let's also include the ``was_published_today`` custom

   300 method from Tutorial 1::

   301 

   302     list_display = ('question', 'pub_date', 'was_published_today')

   303 

   304 Now the poll change list page looks like this:

   305 

   306 .. image:: http://media.djangoproject.com/img/doc/tutorial/admin13t.png

   307    :alt: Polls change list page, updated

   308    :target: http://media.djangoproject.com/img/doc/tutorial/admin13.png

   309 

   310 You can click on the column headers to sort by those values -- except in the

   311 case of the ``was_published_today`` header, because sorting by the output of

   312 an arbitrary method is not supported. Also note that the column header for

   313 ``was_published_today`` is, by default, the name of the method (with

   314 underscores replaced with spaces). But you can change that by giving that

   315 method a ``short_description`` attribute::

   316 

   317     def was_published_today(self):

   318         return self.pub_date.date() == datetime.date.today()

   319     was_published_today.short_description = 'Published today?'

   320 

   321 

   322 Let's add another improvement to the Poll change list page: Filters. Add the

   323 following line to ``Poll.admin``::

   324 

   325     list_filter = ['pub_date']

   326 

   327 That adds a "Filter" sidebar that lets people filter the change list by the

   328 ``pub_date`` field:

   329 

   330 .. image:: http://media.djangoproject.com/img/doc/tutorial/admin14t.png

   331    :alt: Polls change list page, updated

   332    :target: http://media.djangoproject.com/img/doc/tutorial/admin14.png

   333 

   334 The type of filter displayed depends on the type of field you're filtering on.

   335 Because ``pub_date`` is a DateTimeField, Django knows to give the default

   336 filter options for DateTimeFields: "Any date," "Today," "Past 7 days,"

   337 "This month," "This year."

   338 

   339 This is shaping up well. Let's add some search capability::

   340 

   341     search_fields = ['question']

   342 

   343 That adds a search box at the top of the change list. When somebody enters

   344 search terms, Django will search the ``question`` field. You can use as many

   345 fields as you'd like -- although because it uses a ``LIKE`` query behind the

   346 scenes, keep it reasonable, to keep your database happy.

   347 

   348 Finally, because Poll objects have dates, it'd be convenient to be able to

   349 drill down by date. Add this line::

   350 

   351     date_hierarchy = 'pub_date'

   352 

   353 That adds hierarchical navigation, by date, to the top of the change list page.

   354 At top level, it displays all available years. Then it drills down to months

   355 and, ultimately, days.

   356 

   357 Now's also a good time to note that change lists give you free pagination. The

   358 default is to display 50 items per page. Change-list pagination, search boxes,

   359 filters, date-hierarchies and column-header-ordering all work together like you

   360 think they should.

   361 

   362 Customize the admin look and feel

   363 =================================

   364 

   365 Clearly, having "Django administration" and "example.com" at the top of each

   366 admin page is ridiculous. It's just placeholder text.

   367 

   368 That's easy to change, though, using Django's template system. The Django admin

   369 is powered by Django itself, and its interfaces use Django's own template

   370 system. (How meta!)

   371 

   372 Open your settings file (``mysite/settings.py``, remember) and look at the

   373 ``TEMPLATE_DIRS`` setting. ``TEMPLATE_DIRS`` is a tuple of filesystem

   374 directories to check when loading Django templates. It's a search path.

   375 

   376 By default, ``TEMPLATE_DIRS`` is empty. So, let's add a line to it, to tell

   377 Django where our templates live::

   378 

   379     TEMPLATE_DIRS = (

   380         "/home/my_username/mytemplates", # Change this to your own directory.

   381     )

   382 

   383 Now copy the template ``admin/base_site.html`` from within the default Django

   384 admin template directory (``django/contrib/admin/templates``) into an ``admin``

   385 subdirectory of whichever directory you're using in ``TEMPLATE_DIRS``. For

   386 example, if your ``TEMPLATE_DIRS`` includes ``"/home/my_username/mytemplates"``,

   387 as above, then copy ``django/contrib/admin/templates/admin/base_site.html`` to

   388 ``/home/my_username/mytemplates/admin/base_site.html``. Don't forget that

   389 ``admin`` subdirectory.

   390 

   391 Then, just edit the file and replace the generic Django text with your own

   392 site's name and URL as you see fit.

   393 

   394 Note that any of Django's default admin templates can be overridden. To

   395 override a template, just do the same thing you did with ``base_site.html`` --

   396 copy it from the default directory into your custom directory, and make

   397 changes.

   398 

   399 Astute readers will ask: But if ``TEMPLATE_DIRS`` was empty by default, how was

   400 Django finding the default admin templates? The answer is that, by default,

   401 Django automatically looks for a ``templates/`` subdirectory within each app

   402 package, for use as a fallback. See the `loader types documentation`_ for full

   403 information.

   404 

   405 .. _loader types documentation: ../templates_python/#loader-types

   406 

   407 Customize the admin index page

   408 ==============================

   409 

   410 On a similar note, you might want to customize the look and feel of the Django

   411 admin index page.

   412 

   413 By default, it displays all available apps, according to your ``INSTALLED_APPS``

   414 setting. But the order in which it displays things is random, and you may want

   415 to make significant changes to the layout. After all, the index is probably the

   416 most important page of the admin, and it should be easy to use.

   417 

   418 The template to customize is ``admin/index.html``. (Do the same as with

   419 ``admin/base_site.html`` in the previous section -- copy it from the default

   420 directory to your custom template directory.) Edit the file, and you'll see it

   421 uses a template tag called ``{% get_admin_app_list as app_list %}``. That's the

   422 magic that retrieves every installed Django app. Instead of using that, you can

   423 hard-code links to object-specific admin pages in whatever way you think is

   424 best.

   425 

   426 Django offers another shortcut in this department. Run the command

   427 ``python manage.py adminindex polls`` to get a chunk of template code for

   428 inclusion in the admin index template. It's a useful starting point.

   429 

   430 For full details on customizing the look and feel of the Django admin site in

   431 general, see the `Django admin CSS guide`_.

   432 

   433 When you're comfortable with the admin site, read `part 3 of this tutorial`_ to

   434 start working on public poll views.

   435 

   436 .. _Django admin CSS guide: ../admin_css/

   437 .. _part 3 of this tutorial: ../tutorial3/