Django introduction

Introduction to Django

Master in Free Software 2009/2010

Joaquim Rocha <jrocha@igalia.com>

3, July 2010

What is it?

"Django is a highlevel Python Web framework
that encourages rapid development and
clean, pragmatic design."

From Django official website

Master in Free Software | 20092010 2

What is it?

Internal project of Lawrence JournalWorld in
2003
Should help journalists meet fast deadlines
Should not stand in the journalists' way
Got its name after the famous guitarrist
Django Reinhardt


The framework

ObjectRelational Mapper
Automatic Admin Interface
Elegant URL Design
Powerful Template System
i18n

it's amazing...!


Big community

Django has a big community and an extensive list of
Django apps

Search for them in http://code.google.com

Other interesting websites:

* Django sites: http://www.djangosites.org

* Django people: http://www.djangopeople.com


Deployment

FastCGI
mod_python
mod_wsgi
...


DB Backend

Officially supported:

PostgreSQL
MySQL
SQLite
Oracle


Using Django


Installation
Just get a tarball release or checkout the sources:
http://djangoproject.com/download

Then:
# python setup.py install

Or:
# easy_install django


Development


Creating a project
$ djangoadmin.py startproject Project

Project
    __init__.py
    manage.py
    settings.py
    urls.py


Running the project

$ ./manage.py runserver

...and open your browse at localhost:8000


Running the project


Development

Django Projects have Apps

Apps are the projects' components


Creating an App
$ ./manage.py startapp my_app

my_app
    __init__.py
    models.py
    tests.py
    views.py


Building the database

$ ./manage.py syncdb


Project's configuration

Easy configuration in the settings.py file


Building the database

$ ./manage.py syncdb


Development
Django follows the MTV design pattern:

ModelTemplateView


Models
Models are a series of classes describing
objects

They represent the database objects

Never touch SQL again!


Models

class Post(models.Model):

title = models.CharField(max_length = 500)
content = models.TextField()
date = models.DateTimeField(auto_now = True)
...


Views
Views are a series of functions that normally
process some models and render HTML

It's where the magic happens!

How to get all blog posts from the latest 5 days and order them by
descending date?


Views
import datetime

def view_latest_posts(request):
# Last 5 days
date = datetime.datetime.now() -
datetime.timedelta(5)
posts = Post.objects.filter(date__gte =
date).order_by('-
date')

return render_to_response('posts/show_posts.html',
{'posts': posts})


Templates

Will not let you repeat yourself!

Will save designers from the code.


Templates

<html>
<head>
<title>{% block title %}{% endblock %}</title>
</head>
<body>
{% block content %}{% endblock %}
</body>
</html>


Templates
{% extends "base.html" %}

{% block title %}Homepage{% endblock %}

{% block content %}
<h3>This will be some main content</h3>

{% for post in posts %}
<h4>{{ post.title }} on {{ post.date|date:"B d, Y"|
upper }}<h4>

<p>{{ post.content }}</p>
{% endfor %}

{% url project.some_app.views.some_view some arguments %}

{% endblock %}


URLs

In Django, the URLs are part of the design!

urls.py use regular expressions to match URLs
with Views


URLs

urlpatterns = patterns('Project.some_app.views',
(r'^$', 'index'),
(r'^posts/(?P<r_id>d+)/$', 'view_latest_posts'),
(r'^create/$', 'create'),
url(r'^view/post/(?P<p_id>d+)/$', 'view',
name = 'view_post'),
)


Forms

Series of classes that represent an HTML form

Will let you easily configure the expected
type of the inputs, error messages, labels,
etc...


Forms

class CreatePost(forms.Form):
title = forms.CharField(label = "Post Title",
max_length = 500,
widget = forms.TextInput(attrs={
'class': 'big_entry'
}))
content = forms.CharField()
tags = forms.CharField(required = False)


Forms
def create_post(request):
if request.method == 'POST':
form = CreatePost(request.POST)
if form.is_valid():
# Create a new post object with data
# from form.cleaned_data
return HttpResponseRedirect('/index/')
else:
form = CreatePost()

return render_to_response('create.html', {
'form': form,
})


Forms
The quick way:

<form action="/create/"
method="POST">
{{ form.as_p }}
<input type="submit" value="Create"
/>
</form>


Where to go from here?


Django hosts
An extensive list is can be found at:
http://code.djangoproject.com/wiki/DjangoFriendlyWe
bHosts
Popular ones:
http://www.statopia.com/corporate/blog/2007/aug/05/
PopularDjangoHostingService/
Google's AppEngine is also Django friendly:
http://appengine.google.com/


Help
Django Docs

http://docs.djangoproject.com

Some books
● Learning Website Development with Django,
Packt
● Practical Django Projects, Apress
● Pro Django, Apress

Django introduction

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