Jumpstart Django

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

Topics

Topics • What is Django

Topics • What is Django • History of Django

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

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

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

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

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

What is Django?

What is Django? • Not a Gypsy Jazz Guitarist

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

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

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)

It all started HERE Photo by Jeff Croft

Simon Willison Adrian Holovaty

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

Jump to today: Guiding Principles

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

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

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

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

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

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

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

Model View Controller

Model View Controller Model View Template

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

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

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']

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

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)

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)

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

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

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})

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), )

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

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

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>

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)

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

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

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

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

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

Framework Death-match Photo by Bruce Turner

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

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

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

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

Recap

Recap • Django is easy

Recap • Django is easy • Django is fun

Recap • Django is easy • Django is fun • Django scales

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

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

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

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

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

Jumpstart Django

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