django introduction

Introduction to Django

Master in Free Software 2009/2010

Joaquim Rocha <[email protected]>

3, July 2010

Master in Free Software | 20092010 2

What is it?

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

From Django official website


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

http://code.google.com/

http://www.djangosites.org/

http://www.djangopeople.com/


Deployment

FastCGI

mod_python

mod_wsgi

...


DB Backend

Officially supported:

PostgreSQLMySQLSQLiteOracle


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

http://djangoproject.com/download


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?


Viewsimport 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)


Formsdef 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/DjangoFriendlyWebHosts

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

http://docs.djangoproject.com/

django introduction

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