Writing your first Django app, part 7

This tutorial begins where Tutorial 6 left off. We’recontinuing the Web-poll application and will focus on customizing Django’sautomatically-generated admin site that we first explored in Tutorial 2.

Customize the admin form

By registering the Question model with admin.site.register(Question),Django was able to construct a default form representation. Often, you’ll wantto customize how the admin form looks and works. You’ll do this by tellingDjango the options you want when you register the object.

Let’s see how this works by reordering the fields on the edit form. Replacethe admin.site.register(Question) line with:

polls/admin.py

from django.contrib import admin
 
from .models import Question
 
 
class QuestionAdmin(admin.ModelAdmin):
    fields = ['pub_date', 'question_text']
 
admin.site.register(Question, QuestionAdmin)

You’ll follow this pattern – create a model admin class, then pass it as thesecond argument to admin.site.register() – any time you need to change theadmin options for a model.

This particular change above makes the “Publication date” come before the“Question” field:This isn’t impressive with only two fields, but for admin forms with dozensof fields, choosing an intuitive order is an important usability detail.

And speaking of forms with dozens of fields, you might want to split the formup into fieldsets:

polls/admin.py

from django.contrib import admin
 
from .models import Question
 
 
class QuestionAdmin(admin.ModelAdmin):
    fieldsets = [
        (None,               {'fields': ['question_text']}),
        ('Date information', {'fields': ['pub_date']}),
    ]
 
admin.site.register(Question, QuestionAdmin)

The first element of each tuple infieldsets is the title of the fieldset.Here’s what our form looks like now:

Adding related objects

OK, we have our Question admin page, but a Question has multipleChoices, and the admin page doesn’t display choices.

Yet.

There are two ways to solve this problem. The first is to register Choicewith the admin just as we did with Question:

polls/admin.py

from django.contrib import admin
 
from .models import Choice, Question
# ...
admin.site.register(Choice)

Now “Choices” is an available option in the Django admin. The “Add choice” formlooks like this:In that form, the “Question” field is a select box containing every question in thedatabase. Django knows that a ForeignKey should berepresented in the admin as a <select> box. In our case, only one questionexists at this point.

Also note the “Add Another” link next to “Question.” Every object with aForeignKey relationship to another gets this for free. When you click “AddAnother”, you’ll get a popup window with the “Add question” form. If you add a questionin that window and click “Save”, Django will save the question to the database anddynamically add it as the selected choice on the “Add choice” form you’relooking 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 theQuestion object. Let’s make that happen.

Remove the register() call for the Choice model. Then, edit the Questionregistration code to read:

polls/admin.py

from django.contrib import admin
 
from .models import Choice, Question
 
 
class ChoiceInline(admin.StackedInline):
    model = Choice
    extra = 3
 
 
class QuestionAdmin(admin.ModelAdmin):
    fieldsets = [
        (None,               {'fields': ['question_text']}),
        ('Date information', {'fields': ['pub_date'], 'classes': ['collapse']}),
    ]
    inlines = [ChoiceInline]
 
admin.site.register(Question, QuestionAdmin)

This tells Django: “Choice objects are edited on the Question admin page. Bydefault, provide enough fields for 3 choices.”

Load the “Add question” page to see how that looks:It works like this: There are three slots for related Choices – as specifiedby extra – and each time you come back to the “Change” page for analready-created object, you get another three extra slots.

At the end of the three current slots you will find an “Add another Choice”link. If you click on it, a new slot will be added. If you want to remove theadded slot, you can click on the X to the top right of the added slot. Notethat you can’t remove the original three slots. This image shows an added slot:One small problem, though. It takes a lot of screen space to display all thefields for entering related Choice objects. For that reason, Django offers atabular way of displaying inline related objects. To use it, change theChoiceInline declaration to read:

polls/admin.py

class ChoiceInline(admin.TabularInline):
    #...

With that TabularInline (instead of StackedInline), therelated objects are displayed in a more compact, table-based format:Note that there is an extra “Delete?” column that allows removing rows addedusing the “Add Another Choice” button and rows that have already been saved.

Customize the admin change list

Now that the Question admin page is looking good, let’s make some tweaks to the“change list” page – the one that displays all the questions in the system.

Here’s what it looks like at this point:By default, Django displays the str() of each object. But sometimes it’d bemore helpful if we could display individual fields. To do that, use thelist_display admin option, which is atuple of field names to display, as columns, on the change list page for theobject:

polls/admin.py

class QuestionAdmin(admin.ModelAdmin):
    # ...
    list_display = ('question_text', 'pub_date')

For good measure, let’s also include the was_published_recently() methodfrom Tutorial 2:

polls/admin.py

class QuestionAdmin(admin.ModelAdmin):
    # ...
    list_display = ('question_text', 'pub_date', 'was_published_recently')

Now the question change list page looks like this:You can click on the column headers to sort by those values – except in thecase of the was_published_recently header, because sorting by the outputof an arbitrary method is not supported. Also note that the column header forwas_published_recently is, by default, the name of the method (withunderscores replaced with spaces), and that each line contains the stringrepresentation of the output.

You can improve that by giving that method (in polls/models.py) a fewattributes, as follows:

polls/models.py

class Question(models.Model):
    # ...
    def was_published_recently(self):
        now = timezone.now()
        return now - datetime.timedelta(days=1) <= self.pub_date <= now
    was_published_recently.admin_order_field = 'pub_date'
    was_published_recently.boolean = True
    was_published_recently.short_description = 'Published recently?'

For more information on these method properties, seelist_display.

Edit your polls/admin.py file again and add an improvement to theQuestion change list page: filters using thelist_filter. Add the following line toQuestionAdmin:

list_filter = ['pub_date']

That adds a “Filter” sidebar that lets people filter the change list by thepub_date field:The type of filter displayed depends on the type of field you’re filtering on.Because pub_date is a DateTimeField, Djangoknows to give appropriate filter options: “Any date”, “Today”, “Past 7 days”,“This month”, “This year”.

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

search_fields = ['question_text']

That adds a search box at the top of the change list. When somebody enterssearch terms, Django will search the question_text field. You can use as manyfields as you’d like – although because it uses a LIKE query behind thescenes, limiting the number of search fields to a reasonable number will makeit easier for your database to do the search.

Now’s also a good time to note that change lists give you free pagination. Thedefault is to display 100 items per page. Change list pagination, search boxes, filters, date-hierarchies, andcolumn-header-orderingall work together like you think they should.

Customize the admin look and feel

Clearly, having “Django administration” at the top of each admin page isridiculous. It’s just placeholder text.

You can change it, though, using Django’s template system. The Django admin ispowered by Django itself, and its interfaces use Django’s own template system.

Customizing your project’s templates

Create a templates directory in your project directory (the one thatcontains manage.py). Templates can live anywhere on your filesystem thatDjango can access. (Django runs as whatever user your server runs.) However,keeping your templates within the project is a good convention to follow.

Open your settings file (mysite/settings.py, remember) and add aDIRS option in the TEMPLATES setting:

mysite/settings.py

TEMPLATES = [
    {
        'BACKEND': 'django.template.backends.django.DjangoTemplates',
        'DIRS': [os.path.join(BASE_DIR, 'templates')],
        'APP_DIRS': True,
        'OPTIONS': {
            'context_processors': [
                'django.template.context_processors.debug',
                'django.template.context_processors.request',
                'django.contrib.auth.context_processors.auth',
                'django.contrib.messages.context_processors.messages',
            ],
        },
    },
]

DIRS is a list of filesystem directories to checkwhen loading Django templates; it’s a search path.

Organizing templates

Just like the static files, we could have all our templates together, inone big templates directory, and it would work perfectly well. However,templates that belong to a particular application should be placed in thatapplication’s template directory (e.g. polls/templates) rather than theproject’s (templates). We’ll discuss in more detail in thereusable apps tutorialwhy we do this.

Now create a directory called admin inside templates, and copy thetemplate admin/base_site.html from within the default Django admintemplate directory in the source code of Django itself(django/contrib/admin/templates) into that directory.

Where are the Django source files?

If you have difficulty finding where the Django source files are locatedon your system, run the following command:

/

$ python -c "import django; print(django.__path__)"

...\> py -c "import django; print(django.__path__)"

Then, edit the file and replace{{ siteheader|default:('Django administration') }} (including the curlybraces) with your own site’s name as you see fit. You should end up witha section of code like:

{% block branding %}
<h1 id="site-name"><a href="{% url 'admin:index' %}">Polls Administration</a></h1>
{% endblock %}

We use this approach to teach you how to override templates. In an actualproject, you would probably usethe django.contrib.admin.AdminSite.site_header attribute to more easilymake this particular customization.

This template file contains lots of text like {% block branding %}and {{ title }}. The {% and {{ tags are part of Django’stemplate language. When Django renders admin/base_site.html, thistemplate language will be evaluated to produce the final HTML page, just likewe saw in Tutorial 3.

Note that any of Django’s default admin templates can be overridden. Tooverride a template, do the same thing you did with base_site.html – copyit from the default directory into your custom directory, and make changes.

Customizing your application’s templates

Astute readers will ask: But if DIRS was empty bydefault, how was Django finding the default admin templates? The answer isthat, since APP_DIRS is set to True,Django automatically looks for a templates/ subdirectory within eachapplication package, for use as a fallback (don’t forget thatdjango.contrib.admin is an application).

Our poll application is not very complex and doesn’t need custom admintemplates. But if it grew more sophisticated and required modification ofDjango’s standard admin templates for some of its functionality, it would bemore sensible to modify the application’s templates, rather than those in theproject. That way, you could include the polls application in any new projectand be assured that it would find the custom templates it needed.

See the template loading documentation for moreinformation about how Django finds its templates.

Customize the admin index page

On a similar note, you might want to customize the look and feel of the Djangoadmin index page.

By default, it displays all the apps in INSTALLED_APPS that have beenregistered with the admin application, in alphabetical order. You may want tomake significant changes to the layout. After all, the index is probably themost important page of the admin, and it should be easy to use.

The template to customize is admin/index.html. (Do the same as withadmin/base_site.html in the previous section – copy it from the defaultdirectory to your custom template directory). Edit the file, and you’ll see ituses a template variable called app_list. That variable contains everyinstalled Django app. Instead of using that, you can hard-code links toobject-specific admin pages in whatever way you think is best.

What’s next?

The beginner tutorial ends here. In the meantime, you might want to check outsome pointers on where to go from here.

If you are familiar with Python packaging and interested in learning how toturn polls into a “reusable app”, check out Advanced tutorial: How towrite reusable apps.