Rapid Web Application Development With Python/Django

Chamindu R. Munasinghe chamindu@calcey.com@chamindum

Agenda

Python
PyPi & pip
virtualenv
Django
Demo

Python

Open source
Cross platform
General purpose
Dynamic

Python

Object oriented
Procedural
Functional

"Batteries Included"

Python 2.7 vs Python 3

PyPi

Python package index

A repository of around 51k packages

pip

Package manager for Python

              $ pip install django
              $ pip install -r requirements.txt

virtualenv

Isolated working environments

One global python environment

Cannot run multiple python versions

All apps share same packages and versions

Using virtuanenv

virtualenvwrapper

A command line tool to easily manage virtualenv's in development

Django

"The Web framework for perfectionists with deadlines"

Used by

Disqus, Instagram, Pinterest, Bitbucket and many more

Modular

A "project" comprises of many "apps"
Third party apps that can be plugged into a Django project
- Blogs
- Calendars
- CMS's
http://www.djangopackages.com

Architecture

MVT - Model, View, Template
Views are python functions
Built in ORM
Regex based URL patterns
Middleware

Demo

Create a simple "polls" app

Creating the project

$ django-admin.py startproject mysite

Database setup

The app is already configured to use sqlite

Create "polls" app

$ python manage.py startapp polls

Add it to the INSTALLED_APPS

Creating the Models

            class Question(models.Model):
                question_text = models.CharField(max_length=200)
                pub_date = models.DateTimeField('date published')

            class Choice(models.Model):
                question = models.ForeignKey(Question)
                choice_text = models.CharField(max_length=200)
                votes = models.IntegerField(default=0)

Create and apply Migrations

              $ python manage.py makemigrations polls
              $ python manage.py migrate

Exploring the admin app

Basic CRUD operations with zero code

            from django.contrib import admin
            from polls.models import Question
 
            admin.site.register(Question)

Adding "Choices" to the admin

            from django.contrib import admin
            from polls.models import Question, Choice

            class ChoiceInline(admin.StackedInline):
                model = Choice
                extra = 3

            class QuestionAdmin(admin.ModelAdmin):
                inlines = [ChoiceInline]

            admin.site.register(Question, QuestionAdmin)

Creating our first view

            from django.http import HttpResponse

            def index(request):
                return HttpResponse("Hello, world. You're at the polls index.")

URL mapping

            # polls/urls.py
            from django.conf.urls import patterns, url
            from polls import views

            urlpatterns = patterns('', 
                url(r'^$', views.index, name='index'),
            )

            # urls.py
            from django.conf.urls import patterns, include, url
            from django.contrib import admin

            urlpatterns = patterns('',
                url(r'^polls/', include('polls.urls')),
                url(r'^admin/', include(admin.site.urls)),
            )

Using generic views

Generic ListView

            class IndexView(generic.ListView):
                model = Question

Creating a template

            <html>
              <head></head>
              <body>
                <ul>
                  {% for question in object_list %}
                    <li><a href="{% url 'detail' question.id %}">
                    {{ question.question_text }}
                    </a></li>
                  {% empty %}
                    <li>No polls</li>
                  {% endfor %}
                </ul>
              </body>       
            </html>

What we did not cover

More generic views CreateView, UpdateView, DeleteView
Forms
Authentication & Authorization
Middleware
Templates in depth
Caching
Management commands

Hosting Django

nginx and uWSGI recommended

Some interesting tools

django-rest-framework - Easy REST API's
django-crispy-forms - Beautifull looking forms
django-oauth-toolkit - OAuth support
django-debug-toolbar - Debugging tool
django-reversion - Version control for Models
django-guardian - Record level permissions
django-cms - Content management system
django-extentions - Lot of usefull extensions
Celery - Async, distributed job queues

Rapid Web Application Development With Python/Django – Python – PyPi

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Rapid Web Application Development With Python/Django – Python – PyPi

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