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    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: ../tutorial01/
    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 You should see a few other types of editable content, including groups, users
    65 and sites. 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(max_length=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" at the top of each admin page is
    366 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 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: ../tutorial03/
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