/docs/intro/tutorial02.txt

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  1. =====================================
  2. Writing your first Django app, part 2
  3. =====================================
  4. This tutorial begins where :doc:`Tutorial 1 </intro/tutorial01>` left off. We're
  5. continuing the Web-poll application and will focus on Django's
  6. automatically-generated admin site.
  7. .. admonition:: Philosophy
  8. Generating admin sites for your staff or clients to add, change and delete
  9. content is tedious work that doesn't require much creativity. For that
  10. reason, Django entirely automates creation of admin interfaces for models.
  11. Django was written in a newsroom environment, with a very clear separation
  12. between "content publishers" and the "public" site. Site managers use the
  13. system to add news stories, events, sports scores, etc., and that content is
  14. displayed on the public site. Django solves the problem of creating a
  15. unified interface for site administrators to edit content.
  16. The admin isn't necessarily intended to be used by site visitors; it's for
  17. site managers.
  18. Activate the admin site
  19. =======================
  20. The Django admin site is not activated by default -- it's an opt-in thing. To
  21. activate the admin site for your installation, do these three things:
  22. * Add ``"django.contrib.admin"`` to your :setting:`INSTALLED_APPS` setting.
  23. * Run ``python manage.py syncdb``. Since you have added a new application
  24. to :setting:`INSTALLED_APPS`, the database tables need to be updated.
  25. * Edit your ``mysite/urls.py`` file and uncomment the lines that reference
  26. the admin -- there are three lines in total to uncomment. This file is a
  27. URLconf; we'll dig into URLconfs in the next tutorial. For now, all you
  28. need to know is that it maps URL roots to applications. In the end, you
  29. should have a ``urls.py`` file that looks like this:
  30. .. parsed-literal::
  31. from django.conf.urls.defaults import *
  32. # Uncomment the next two lines to enable the admin:
  33. **from django.contrib import admin**
  34. **admin.autodiscover()**
  35. urlpatterns = patterns('',
  36. # Example:
  37. # (r'^mysite/', include('mysite.foo.urls')),
  38. # Uncomment the admin/doc line below and add 'django.contrib.admindocs'
  39. # to INSTALLED_APPS to enable admin documentation:
  40. # (r'^admin/doc/', include('django.contrib.admindocs.urls')),
  41. # Uncomment the next line to enable the admin:
  42. **(r'^admin/', include(admin.site.urls)),**
  43. )
  44. (The bold lines are the ones that needed to be uncommented.)
  45. Start the development server
  46. ============================
  47. Let's start the development server and explore the admin site.
  48. Recall from Tutorial 1 that you start the development server like so:
  49. .. code-block:: bash
  50. python manage.py runserver
  51. Now, open a Web browser and go to "/admin/" on your local domain -- e.g.,
  52. http://127.0.0.1:8000/admin/. You should see the admin's login screen:
  53. .. image:: _images/admin01.png
  54. :alt: Django admin login screen
  55. Enter the admin site
  56. ====================
  57. Now, try logging in. (You created a superuser account in the first part of this
  58. tutorial, remember? If you didn't create one or forgot the password you can
  59. :ref:`create another one <topics-auth-creating-superusers>`.) You should see
  60. the Django admin index page:
  61. .. image:: _images/admin02t.png
  62. :alt: Django admin index page
  63. You should see a few other types of editable content, including groups, users
  64. and sites. These are core features Django ships with by default.
  65. Make the poll app modifiable in the admin
  66. =========================================
  67. But where's our poll app? It's not displayed on the admin index page.
  68. Just one thing to do: We need to tell the admin that ``Poll``
  69. objects have an admin interface. To do this, create a file called
  70. ``admin.py`` in your ``polls`` directory, and edit it to look like this::
  71. from polls.models import Poll
  72. from django.contrib import admin
  73. admin.site.register(Poll)
  74. You'll need to restart the development server to see your changes. Normally,
  75. the server auto-reloads code every time you modify a file, but the action of
  76. creating a new file doesn't trigger the auto-reloading logic.
  77. Explore the free admin functionality
  78. ====================================
  79. Now that we've registered ``Poll``, Django knows that it should be displayed on
  80. the admin index page:
  81. .. image:: _images/admin03t.png
  82. :alt: Django admin index page, now with polls displayed
  83. Click "Polls." Now you're at the "change list" page for polls. This page
  84. displays all the polls in the database and lets you choose one to change it.
  85. There's the "What's up?" poll we created in the first tutorial:
  86. .. image:: _images/admin04t.png
  87. :alt: Polls change list page
  88. Click the "What's up?" poll to edit it:
  89. .. image:: _images/admin05t.png
  90. :alt: Editing form for poll object
  91. Things to note here:
  92. * The form is automatically generated from the Poll model.
  93. * The different model field types (:class:`~django.db.models.DateTimeField`,
  94. :class:`~django.db.models.CharField`) correspond to the appropriate HTML
  95. input widget. Each type of field knows how to display itself in the Django
  96. admin.
  97. * Each :class:`~django.db.models.DateTimeField` gets free JavaScript
  98. shortcuts. Dates get a "Today" shortcut and calendar popup, and times get
  99. a "Now" shortcut and a convenient popup that lists commonly entered times.
  100. The bottom part of the page gives you a couple of options:
  101. * Save -- Saves changes and returns to the change-list page for this type of
  102. object.
  103. * Save and continue editing -- Saves changes and reloads the admin page for
  104. this object.
  105. * Save and add another -- Saves changes and loads a new, blank form for this
  106. type of object.
  107. * Delete -- Displays a delete confirmation page.
  108. Change the "Date published" by clicking the "Today" and "Now" shortcuts. Then
  109. click "Save and continue editing." Then click "History" in the upper right.
  110. You'll see a page listing all changes made to this object via the Django admin,
  111. with the timestamp and username of the person who made the change:
  112. .. image:: _images/admin06t.png
  113. :alt: History page for poll object
  114. Customize the admin form
  115. ========================
  116. Take a few minutes to marvel at all the code you didn't have to write. By
  117. registering the Poll model with ``admin.site.register(Poll)``, Django was able
  118. to construct a default form representation. Often, you'll want to customize how
  119. the admin form looks and works. You'll do this by telling Django the options
  120. you want when you register the object.
  121. Let's see how this works by re-ordering the fields on the edit form. Replace
  122. the ``admin.site.register(Poll)`` line with::
  123. class PollAdmin(admin.ModelAdmin):
  124. fields = ['pub_date', 'question']
  125. admin.site.register(Poll, PollAdmin)
  126. You'll follow this pattern -- create a model admin object, then pass it as the
  127. second argument to ``admin.site.register()`` -- any time you need to change the
  128. admin options for an object.
  129. This particular change above makes the "Publication date" come before the
  130. "Question" field:
  131. .. image:: _images/admin07.png
  132. :alt: Fields have been reordered
  133. This isn't impressive with only two fields, but for admin forms with dozens
  134. of fields, choosing an intuitive order is an important usability detail.
  135. And speaking of forms with dozens of fields, you might want to split the form
  136. up into fieldsets::
  137. class PollAdmin(admin.ModelAdmin):
  138. fieldsets = [
  139. (None, {'fields': ['question']}),
  140. ('Date information', {'fields': ['pub_date']}),
  141. ]
  142. admin.site.register(Poll, PollAdmin)
  143. The first element of each tuple in ``fieldsets`` is the title of the fieldset.
  144. Here's what our form looks like now:
  145. .. image:: _images/admin08t.png
  146. :alt: Form has fieldsets now
  147. You can assign arbitrary HTML classes to each fieldset. Django provides a
  148. ``"collapse"`` class that displays a particular fieldset initially collapsed.
  149. This is useful when you have a long form that contains a number of fields that
  150. aren't commonly used::
  151. class PollAdmin(admin.ModelAdmin):
  152. fieldsets = [
  153. (None, {'fields': ['question']}),
  154. ('Date information', {'fields': ['pub_date'], 'classes': ['collapse']}),
  155. ]
  156. .. image:: _images/admin09.png
  157. :alt: Fieldset is initially collapsed
  158. Adding related objects
  159. ======================
  160. OK, we have our Poll admin page. But a ``Poll`` has multiple ``Choices``, and
  161. the admin page doesn't display choices.
  162. Yet.
  163. There are two ways to solve this problem. The first is to register ``Choice``
  164. with the admin just as we did with ``Poll``. That's easy::
  165. from polls.models import Choice
  166. admin.site.register(Choice)
  167. Now "Choices" is an available option in the Django admin. The "Add choice" form
  168. looks like this:
  169. .. image:: _images/admin10.png
  170. :alt: Choice admin page
  171. In that form, the "Poll" field is a select box containing every poll in the
  172. database. Django knows that a :class:`~django.db.models.ForeignKey` should be
  173. represented in the admin as a ``<select>`` box. In our case, only one poll
  174. exists at this point.
  175. Also note the "Add Another" link next to "Poll." Every object with a
  176. ``ForeignKey`` relationship to another gets this for free. When you click "Add
  177. Another," you'll get a popup window with the "Add poll" form. If you add a poll
  178. in that window and click "Save," Django will save the poll to the database and
  179. dynamically add it as the selected choice on the "Add choice" form you're
  180. looking at.
  181. But, really, this is an inefficient way of adding Choice objects to the system.
  182. It'd be better if you could add a bunch of Choices directly when you create the
  183. Poll object. Let's make that happen.
  184. Remove the ``register()`` call for the Choice model. Then, edit the ``Poll``
  185. registration code to read::
  186. class ChoiceInline(admin.StackedInline):
  187. model = Choice
  188. extra = 3
  189. class PollAdmin(admin.ModelAdmin):
  190. fieldsets = [
  191. (None, {'fields': ['question']}),
  192. ('Date information', {'fields': ['pub_date'], 'classes': ['collapse']}),
  193. ]
  194. inlines = [ChoiceInline]
  195. admin.site.register(Poll, PollAdmin)
  196. This tells Django: "Choice objects are edited on the Poll admin page. By
  197. default, provide enough fields for 3 choices."
  198. Load the "Add poll" page to see how that looks, you may need to restart your development server:
  199. .. image:: _images/admin11t.png
  200. :alt: Add poll page now has choices on it
  201. It works like this: There are three slots for related Choices -- as specified
  202. by ``extra`` -- and each time you come back to the "Change" page for an
  203. already-created object, you get another three extra slots.
  204. One small problem, though. It takes a lot of screen space to display all the
  205. fields for entering related Choice objects. For that reason, Django offers a
  206. tabular way of displaying inline related objects; you just need to change
  207. the ``ChoiceInline`` declaration to read::
  208. class ChoiceInline(admin.TabularInline):
  209. #...
  210. With that ``TabularInline`` (instead of ``StackedInline``), the
  211. related objects are displayed in a more compact, table-based format:
  212. .. image:: _images/admin12.png
  213. :alt: Add poll page now has more compact choices
  214. Customize the admin change list
  215. ===============================
  216. Now that the Poll admin page is looking good, let's make some tweaks to the
  217. "change list" page -- the one that displays all the polls in the system.
  218. Here's what it looks like at this point:
  219. .. image:: _images/admin04t.png
  220. :alt: Polls change list page
  221. By default, Django displays the ``str()`` of each object. But sometimes it'd be
  222. more helpful if we could display individual fields. To do that, use the
  223. ``list_display`` admin option, which is a tuple of field names to display, as
  224. columns, on the change list page for the object::
  225. class PollAdmin(admin.ModelAdmin):
  226. # ...
  227. list_display = ('question', 'pub_date')
  228. Just for good measure, let's also include the ``was_published_today`` custom
  229. method from Tutorial 1::
  230. class PollAdmin(admin.ModelAdmin):
  231. # ...
  232. list_display = ('question', 'pub_date', 'was_published_today')
  233. Now the poll change list page looks like this:
  234. .. image:: _images/admin13t.png
  235. :alt: Polls change list page, updated
  236. You can click on the column headers to sort by those values -- except in the
  237. case of the ``was_published_today`` header, because sorting by the output of
  238. an arbitrary method is not supported. Also note that the column header for
  239. ``was_published_today`` is, by default, the name of the method (with
  240. underscores replaced with spaces). But you can change that by giving that
  241. method (in ``models.py``) a ``short_description`` attribute::
  242. def was_published_today(self):
  243. return self.pub_date.date() == datetime.date.today()
  244. was_published_today.short_description = 'Published today?'
  245. Edit your admin.py file again and add an improvement to the Poll change list page: Filters. Add the
  246. following line to ``PollAdmin``::
  247. list_filter = ['pub_date']
  248. That adds a "Filter" sidebar that lets people filter the change list by the
  249. ``pub_date`` field:
  250. .. image:: _images/admin14t.png
  251. :alt: Polls change list page, updated
  252. The type of filter displayed depends on the type of field you're filtering on.
  253. Because ``pub_date`` is a DateTimeField, Django knows to give the default
  254. filter options for DateTimeFields: "Any date," "Today," "Past 7 days,"
  255. "This month," "This year."
  256. This is shaping up well. Let's add some search capability::
  257. search_fields = ['question']
  258. That adds a search box at the top of the change list. When somebody enters
  259. search terms, Django will search the ``question`` field. You can use as many
  260. fields as you'd like -- although because it uses a ``LIKE`` query behind the
  261. scenes, keep it reasonable, to keep your database happy.
  262. Finally, because Poll objects have dates, it'd be convenient to be able to
  263. drill down by date. Add this line::
  264. date_hierarchy = 'pub_date'
  265. That adds hierarchical navigation, by date, to the top of the change list page.
  266. At top level, it displays all available years. Then it drills down to months
  267. and, ultimately, days.
  268. Now's also a good time to note that change lists give you free pagination. The
  269. default is to display 50 items per page. Change-list pagination, search boxes,
  270. filters, date-hierarchies and column-header-ordering all work together like you
  271. think they should.
  272. Customize the admin look and feel
  273. =================================
  274. Clearly, having "Django administration" at the top of each admin page is
  275. ridiculous. It's just placeholder text.
  276. That's easy to change, though, using Django's template system. The Django admin
  277. is powered by Django itself, and its interfaces use Django's own template
  278. system.
  279. Open your settings file (``mysite/settings.py``, remember) and look at the
  280. :setting:`TEMPLATE_DIRS` setting. :setting:`TEMPLATE_DIRS` is a tuple of
  281. filesystem directories to check when loading Django templates. It's a search
  282. path.
  283. By default, :setting:`TEMPLATE_DIRS` is empty. So, let's add a line to it, to
  284. tell Django where our templates live::
  285. TEMPLATE_DIRS = (
  286. '/home/my_username/mytemplates', # Change this to your own directory.
  287. )
  288. Now copy the template ``admin/base_site.html`` from within the default Django
  289. admin template directory in the source code of Django itself
  290. (``django/contrib/admin/templates``) into an ``admin`` subdirectory of
  291. whichever directory you're using in :setting:`TEMPLATE_DIRS`. For example, if
  292. your :setting:`TEMPLATE_DIRS` includes ``'/home/my_username/mytemplates'``, as
  293. above, then copy ``django/contrib/admin/templates/admin/base_site.html`` to
  294. ``/home/my_username/mytemplates/admin/base_site.html``. Don't forget that
  295. ``admin`` subdirectory.
  296. Then, just edit the file and replace the generic Django text with your own
  297. site's name as you see fit.
  298. This template file contains lots of text like ``{% block branding %}``
  299. and ``{{ title }}``. The ``{%`` and ``{{`` tags are part of Django's
  300. template language. When Django renders ``admin/base_site.html``, this
  301. template language will be evaluated to produce the final HTML page.
  302. Don't worry if you can't make any sense of the template right now --
  303. we'll delve into Django's templating language in Tutorial 3.
  304. Note that any of Django's default admin templates can be overridden. To
  305. override a template, just do the same thing you did with ``base_site.html`` --
  306. copy it from the default directory into your custom directory, and make
  307. changes.
  308. Astute readers will ask: But if :setting:`TEMPLATE_DIRS` was empty by default,
  309. how was Django finding the default admin templates? The answer is that, by
  310. default, Django automatically looks for a ``templates/`` subdirectory within
  311. each app package, for use as a fallback. See the :ref:`template loader
  312. documentation <template-loaders>` for full information.
  313. Customize the admin index page
  314. ==============================
  315. On a similar note, you might want to customize the look and feel of the Django
  316. admin index page.
  317. By default, it displays all the apps in :setting:`INSTALLED_APPS` that have been
  318. registered with the admin application, in alphabetical order. You may want to
  319. make significant changes to the layout. After all, the index is probably the
  320. most important page of the admin, and it should be easy to use.
  321. The template to customize is ``admin/index.html``. (Do the same as with
  322. ``admin/base_site.html`` in the previous section -- copy it from the default
  323. directory to your custom template directory.) Edit the file, and you'll see it
  324. uses a template variable called ``app_list``. That variable contains every
  325. installed Django app. Instead of using that, you can hard-code links to
  326. object-specific admin pages in whatever way you think is best. Again,
  327. don't worry if you can't understand the template language -- we'll cover that
  328. in more detail in Tutorial 3.
  329. When you're comfortable with the admin site, read :doc:`part 3 of this tutorial
  330. </intro/tutorial03>` to start working on public poll views.