Short Django Tutorial Notes

Some condensed notes on the Django tutorial (Django 1.3) This is just a short self-reference (or maybe a 2-minute overview), not an actual tutorial.

Database

Create / update database

python manage.py syncdb

Models

Models define how data is stored. Create a model by inheriting from django.db.models.Model

from django.db import models
 
class Choice(models.Model):
    poll = models.ForeignKey(Poll)
    choice = models.CharField(max_length=200)
    votes = models.IntegerField()
    def __unicode__(self):
        return self.choice

App

An “app” is simply a directory with an __init__.py file and other python files. (An “app” is more commonly known in other languages as a “package”.)

The INSTALLED_APPS variable in settings.py tells Django which apps to use.

INSTALLED_APPS = (
    'django.contrib.auth',
    'django.contrib.contenttypes',
    'django.contrib.sessions',
    'django.contrib.sites',
    'polls'
)

Make sure your app directory is on your Python path.

Re-run python manage.py syncdb after making changes to the INSTALLED_APPS.

URLs

The variable urlpatterns tells Django which Python code to run (which view to use) based on the url path.

from django.conf.urls.defaults import patterns, include, url
from django.contrib import admin
admin.autodiscover()
 
urlpatterns = patterns('',
   (r'^polls/$', 'polls.views.index'),
   (r'^polls/(?P
<poll_id>\d+)/$', 'polls.views.detail'),
   url(r'^admin/', include(admin.site.urls)),
)

The ROOT_URLCONF variable in settings.py tells Django where to find the module-level variable urlpatterns. E.g. if urlpatterns is defined in mysite/urls.py, the settings.py file should have

ROOT_URLCONF = 'mysite.urls'

View

The code used to generate a page is called a view. A view is a Python function which returns a web page. Example index() view in polls/views.py

from django.template import Context, loader
from polls.models import Poll
from django.http import HttpResponse
 
def index(request):
    latest_poll_list = Poll.objects.all().order_by('-pub_date')[:5]
    t = loader.get_template('polls/index.html')
    c = Context({
        'latest_poll_list': latest_poll_list,
    })
    return HttpResponse(t.render(c))

The urlpatterns tells Django which view to use based on the url. For example, the urlpatterns line

   (r'^polls/$', 'polls.views.index'),

tells Django that the url http://site.com/polls is created by the index() function in polls/views.py.

render_to_response is a common shortcut for creating views. Equivalent view using render_to_response

from django.shortcuts import render_to_response
from polls.models import Poll
 
def index(request):
    latest_poll_list = Poll.objects.all().order_by('-pub_date')[:5]
    return render_to_response('polls/index.html', {'latest_poll_list': latest_poll_list})

Often views need to respond to a request. Templates use the {% csrf_token %} to prevent “Cross Site Request Forgeries”, and the view uses a django.template.RequestContext

from django.template import RequestContext
# ...
def detail(request, poll_id):
    p = get_object_or_404(Poll, pk=poll_id)
    return render_to_response('polls/detail.html', {'poll': p},
                               context_instance=RequestContext(request))

Template

A Django template is a HTML skeleton with special Django tags which tell the Django view where to fill in data. Example template polls/index.html

{% if latest_poll_list %}
<ul>
    {% for poll in latest_poll_list %}
<li><a href="/polls/{{ poll.id }}/">{{ poll.question }}</a></li>
 
    {% endfor %}
    </ul>
 
{% else %}
    <p>No polls are available.</p>
{% endif %}

Admin Interface

from polls.models import Poll
from django.contrib import admin
 
class PollAdmin(admin.ModelAdmin):
    fields = ['pub_date', 'question']
 
admin.site.register(Poll, PollAdmin)

Generic Views

There’s generic views which means that you don’t have to write a view function; you use django.views.generic to generate a simple view.

from django.conf.urls.defaults import patterns, include, url
from django.views.generic import DetailView, ListView
from polls.models import Poll
 
urlpatterns = patterns('',
    (r'^$',
        ListView.as_view(
            queryset=Poll.objects.order_by('-pub_date')[:5],
            context_object_name='latest_poll_list',
            template_name='polls/index.html')),
    (r'^(?P
<pk>\d+)/$',
        DetailView.as_view(
            model=Poll,
            template_name='polls/detail.html')),
    url(r'^(?P
<pk>\d+)/results/$',
        DetailView.as_view(
            model=Poll,
            template_name='polls/results.html'),
        name='poll_results'),
    (r'^(?P
<poll_id>\d+)/vote/$', 'polls.views.vote'),
)