An overview of the Django rapid application development framework. Topics include the history of the framework, an architectural overview, how to get started, and a brief comparison to Ruby on Rails.

1. Jumpstart
The Web Framework
for Perfectionists with Deadlines
CPOSC
Rob Yates October, 2009

2. Topics

3. Topics
• What is Django

4. Topics
• What is Django
• History of Django

5. Topics
• What is Django
• History of Django
• Whirlwind Tour

6. Topics
• What is Django
• History of Django
• Whirlwind Tour
• How to Get Started - Admin Demo

7. Topics
• What is Django
• History of Django
• Whirlwind Tour
• How to Get Started - Admin Demo
• Killer Features

8. Topics
• What is Django
• History of Django
• Whirlwind Tour
• How to Get Started - Admin Demo
• Killer Features
• Application Re-use and Pinax

9. Topics
• What is Django
• History of Django
• Whirlwind Tour
• How to Get Started - Admin Demo
• Killer Features
• Application Re-use and Pinax
• Framework Death-match

10. What is Django?

11. What is Django?
• Not a Gypsy Jazz Guitarist

12. What is Django?
• Not a Gypsy Jazz Guitarist
• Web Application
Development Framework
written in and for Python

13. What is Django?
• Not a Gypsy Jazz Guitarist
• Web Application
Development Framework
written in and for Python
• Not a CMS System

14. What is Django?
• Not a Gypsy Jazz Guitarist
• Web Application
Development Framework
written in and for Python
• Not a CMS System
• Sometimes called Python’s
Ruby on Rails (RoR)

15. It all started
HERE
Photo by Jeff Croft

16. Simon Willison
Adrian Holovaty

18. PyCon 2005
Major topic: Why is web development
in Python so hard?

19. Jump to today:
Guiding Principles

20. Jump to today:
Guiding Principles
• Loose Coupling and tight cohesion

21. Jump to today:
Guiding Principles
• Loose Coupling and tight cohesion
• Less code

22. Jump to today:
Guiding Principles
• Loose Coupling and tight cohesion
• Less code
• Quick development

23. Jump to today:
Guiding Principles
• Loose Coupling and tight cohesion
• Less code
• Quick development
• DRY

24. Jump to today:
Guiding Principles
• Loose Coupling and tight cohesion
• Less code
• Quick development
• DRY
• Explicit is better than implicit

25. Jump to today:
Guiding Principles
• Loose Coupling and tight cohesion
• Less code
• Quick development
• DRY
• Explicit is better than implicit
• Consistency

26. For Free!!!
• Very Useful Admin CRUD
• Templating - lots of useful rendering bits
• Form Handling
• i18n - full Unicode support
• Sessions / User Auth / Role-based Perms
• Object-Relational Mapping
Beer photo by Lori Spindler

27. Model View Controller

28. Model View Controller
Model
View
Template

29. Models
Templates
App
Views
Models
Templates
App
Views
Site
Models
Templates
App
Views
Settings
URLs
Django App Structure
Templates

30. Architecture
RDBMS
Storage ORM Fixtures
Model
Signals Forms Template
URL Resolver View Template Loader
Middleware Middleware
Request Response

31. Deep Dive: Models
from tagging.fields import TagField
class Post(models.Model):
author = models.ForeignKey(Author)
title = models.CharField(max_length=200)
slug = models.SlugField(max_length=200, unique_for_month='pub_date')
body = models.TextField()
TYPE_CHOICES = (
('rant', 'Rant'),
('tirade', 'Tirade'),
)
type = models.CharField(choices=TYPE_CHOICES, max_length=50)
pub_date = models.DateTimeField(auto_now_add=True)
is_active = models.BooleanField(default=True)
tags = TagField(blank=True, null=True)
class Meta:
unique_together = ('title', 'type')
ordering = ['-pub_date']

32. Architecture
RDBMS
Storage ORM Fixtures
Model
Signals Forms Template
URL Resolver View Template Loader
Middleware Middleware
Request Response

33. Deep Dive: DB API
post = Post(title=‘Foo’, body=‘Bar’)
post.type = ‘rant’
post.save()

34. Deep Dive: DB API
post = Post(title=‘Foo’, body=‘Bar’)
post.type = ‘rant’
post.save()
posts = Post.objects.all()
posts = Post.objects.all()[:5]
posts = Post.objects.filter(post_type=‘rant’)
posts = Post.objects.filter(author__name=‘Rob’)
posts = Post.objects.filter(author__name=‘Rob’).
filter(title__contains=‘django’).order_by(‘type’)
post = Post.objects.get(id=24)

35. Architecture
RDBMS
Storage ORM Fixtures
Model
Signals Forms Template
URL Resolver View Template Loader
Middleware Middleware
Request Response

36. Deep Dive: Forms
# Basic Form
class ContactForm(forms.Form):
subject = forms.CharField(max_length=100)
message = forms.CharField()
sender = forms.EmailField()
cc_myself = forms.BooleanField(required=False)

37. Deep Dive: Forms
# Basic Form
class ContactForm(forms.Form):
subject = forms.CharField(max_length=100)
message = forms.CharField()
sender = forms.EmailField()
cc_myself = forms.BooleanField(required=False)
# Form based on a model
class PostForm(forms.ModelForm):
class Meta:
model = Post

38. Deep Dive: Views
def posts_by_type(request, type):
posts = Post.objects.filter(type=type)
return render_to_response(
‘postsbytype.html’, {‘posts’: posts})

39. Deep Dive: Views
def posts_by_type(request, type):
posts = Post.objects.filter(type=type)
return render_to_response(
‘postsbytype.html’, {‘posts’: posts})
def new_post(request):
if request.method == ‘POST’:
form = PostForm(request.POST)
if form.is_valid():
form.save()
else:
form = PostForm()
return render_to_response(
‘mytemplate.html’, {‘form’: form})

40. Architecture
RDBMS
Storage ORM Fixtures
Model
Signals Forms Template
URL Resolver View Template Loader
Middleware Middleware
Request Response

41. Deep Dive: URLs
urlpatters = patterns(‘’,
(’^my/favorite/color/$’, ‘blog.views.my_fav_color’),
(‘^post/new/$’, ‘blog.views.new_post’),
(‘^posts/(d{4})/$’, ‘blog.views.year_archive’),
(‘^posts/(d{4})/(d{2})/$’, ‘blog.views.month_archive’),
(‘^posts/(?P<slug>[a-z-]*)/$’, ‘blog.views.show_post’),
(‘^events/$’, include(events.urls),
)

42. Architecture
RDBMS
Storage ORM Fixtures
Model
Signals Forms Template
URL Resolver View Template Loader
Middleware Middleware
Request Response

43. Architecture
RDBMS
Storage ORM Fixtures
Model
Signals Forms Template
URL Resolver View Template Loader
Middleware Middleware
Request Response

44. Deep Dive: Templates
<html><body>
{% if posts %}
{% for post in posts %}
{{ post.author }}: {{ post.title }}
{% endfor %}
{% endif %}

45. Deep Dive: Templates
<html><body>
{% if posts %}
{% for post in posts %}
{{ post.author }}: {{ post.title }}
{% endfor %}
{% endif %}
<form method=”post”>
<table>
{{ form }}
</table>
</form>

46. Deep Dive: Templates
<html><body>
{% if posts %}
{% for post in posts %}
{{ post.author }}: {{ post.title }}
{% endfor %}
{% endif %}
<form method=”post”>
<ul>
{{ form.as_ul }}
</ul>
</form>

47. Architecture
RDBMS
Storage ORM Fixtures
Model
Signals Forms Template
URL Resolver View Template Loader
Middleware Middleware
Request Response

48. Getting Started
• Pure Python - no compiled code
• No dependencies (with the exception of
the database adapter of your choice
• Three-step install
• D/L and extract tar
• Run setup.py
• Add django-admin.py to path (optional)

49. Initialize Your Project
$ django-admin.py startproject mysite
$ cd mysite
$ python manage.py startapp myapp
$ edit settings.py and set DB Info
$ python manage.py runserver
http://localhost:8000

50. Killer Features
• Legacy DB • Generic Views
• Test Framework • Template Inheritance
• Multi-DB • Tempalte Filters
• Geodjango • Humanize
• Aggregation • Runs on Jython /
IronPython
• JSON Serializer
• Stable API Promise • Google AppEngine!
• Fantastic Docs

51. Roll Your Own
• Model Managers: Custom database API for views
• Custom Template Tags: Easier to implement
functionality without mixing logic/presentation

52. Roll Your Own
• Model Managers: Custom database API for views
• Custom Template Tags: Easier to implement
functionality without mixing logic/presentation
• ORM Layer • Model Fields
• Template Engine • Form Fields
• Template Loader • URL Resolver

53. Re-usable Apps
and Pinax
• Following best practices when creating
your app allows others to plug in and use it
• Search Google Code for *django* projects
returns 1,987 results - many are apps
• James Tauber created Django Hotclub to
establish standards for app development
and integration
• Hotclub later become Pinax

55. Framework Death-match
Photo by Bruce Turner

56. Death-match: RoR
• URL Handling
• RoR: RESTful with HTTP verbs
• Django: RegEx-based URL patterns
• JavaScript / AJAX
• RoR: XHR helpers with RJS, prototype, scriptaculous
• Django: JS framework agnostic / no helpers besides
serialization

57. Death-match: RoR
• Unicode
• Ruby traditionally has had issues - string is byte sequence
• Python is fully Unicode since v1.6 (circa 2000)
• i18n
• RoR: Translations are copied - no fallback?
• Django: Translations use GNU gettext-style localization -
falls back to default language

58. Death-match: RoR
• Plugins
• RoR: Rich plugin API and structure
• Django: Re-usable applications
• Automation / Build
• RoR: rake is a rich scripting language for automated tasks
• Django: manage.py can do some basic tricks - CLI

59. Death-match: RoR
• Jobs: Rails jobs out-number Django jobs 6:1
• Hype: Rails has done a fantastic job with marketing

60. Death-match: RoR
• Jobs: Rails jobs out-number Django jobs 6:1
• Hype: Rails has done a fantastic job with marketing

61. Recap

62. Recap
• Django is easy

63. Recap
• Django is easy
• Django is fun

64. Recap
• Django is easy
• Django is fun
• Django scales

65. Recap
• Django is easy
• Django is fun
• Django scales
• Django is maintainable

66. Recap
• Django is easy
• Django is fun
• Django scales
• Django is maintainable
• Django saves small kittens

67. Recap
• Django is easy
• Django is fun
• Django scales
• Django is maintainable
• Django saves small kittens
• It rocks - USE IT!

68. Resources
• http://djangoproject.com
• Check out the tutorial!
• http://docs.djangoproject.com
• http://djangodose.com
• http://www.b-list.org/
• http://pinaxproject.com
• http://code.google.com/hosting/search?
q=label%3aDjango

69. Thanks!
rob@robyates.org
Twitter: @Rob_Yates
http://robyates.org