Introduction to Django
Welcome! In this book, you will learn about Django, an Open Source web framework
that enables you to build clean and feature-rich web applications with minimal
time and effort. Django is written in Python, a general purpose language that is
well suited for developing web applications. Django loosely follows a model-viewcontroller
design pattern, which greatly helps in building clean and maintainable
This chapter gives you an overview of the technologies used in this book. The
following chapters will take you through a tutorial for building a social bookmarking
application from the group using Django.
In this introduction, you will read about the following:
* The MVC pattern in web development.
* Why we should use Python.
* Why we should use Django.
* The history of Django.
The MVC Pattern in Web Development
Web development has made great progress during the last few years. It began as a
tedious task that involved using CGI for interfacing external programs with the web
server. CGI applications used standard I/O facilities available to the C programming
language in order to manually parse user input and produce page output. In
addition to being diffi cult to work with, CGI required a separate copy of the program
to be launched for each request, which used to quickly overwhelm servers.
Next, scripting languages were introduced to web development, and this inspired
developers to create more efficient technologies. Languages such as Perl and PHP
quickly made their way into the world of web development, and as a result,
common web tasks such as cookie handling, session management, and text
processing became much easier. Although scripting languages included libraries to
deal with day-to-day web-related tasks, they lacked unifi ed frameworks, as libraries
were usually disparate in design, usage, and conventions. Therefore, the need for
cohesive frameworks arose.
A few years ago, the model-view-controller pattern came for web-based applications
was introduced. This software engineering pattern separates data (model), user
interface (view), and data handling logic (controller), so that one can be changed
without affecting the others. The benefi ts of this pattern are obvious. With it,
designers can work on the interface without worrying about data storage or
management. And developers are able to program the logic of data handling without
getting into the details of presentation. As a result, the MVC pattern quickly found
its way into web languages, and serious web developers started to embrace it in
preference to previous techniques.
The diagram below shows how each of the components of the MVC pattern interact
with each other to serve a user request:
Python is a general purpose programming language. Although it is used for a wide
variety of applications, Python is very suitable for developing web applications. It
has a clean and elegant syntax, and is supported by a large library of standard
and contributed modules, which covers everything from multi-threading to the
zipping of fi les. The language’s object-oriented model is especially suited for MVC
Sooner or later, performance will become a major concern with web projects, and
Python’s runtime environment shines here, as it is known to be fast and stable.
Python supports a wide range of web servers through modules, including the
infamous Apache. Furthermore, it is available for all the major platforms: UNIX/
Linux, Windows, and Mac. Python also supports a wide array of database servers,
but you won’t have to deal directly with them; Django provides a unifi ed layer of
access to all available database engines, as we will see later.
Python is free software; you can download and use it freely from
http://python.org/. You are even allowed to distribute it without having
to pay any fees. Access to the source code is available to those who want to add
features or fi x bugs. As a result, Python enjoys a large community of developers
who quickly fi x bugs and introduce new features.
Python is very easy to learn, and it is being adopted in many universities as the
fi rst programming language to be taught. Although this book assumes working
knowledge of Python, advanced features will be explained as they are used. If you
want to refresh your Python knowledge, you are recommended to read the official
Python tutorial available at http://python.org/doc/ before continuing with
To sum up, Python was chosen over many other scripting languages for this book for
the following reasons:
- Clean and elegant syntax.
- Large standard library of modules that covers a wide range of tasks.
- Extensive documentation.
- Mature runtime environment.
- Support for standard and proven technologies such as Linux and Apache.
S ince the spread of the MVC pattern into web development, Python has provided
quite a few choices when it comes to web frameworks, such as Django, TurboGears
and Zope. Although choosing one out of many can be confusing at fi rst, having
several competing frameworks can only be a good thing for the Python community,
as it drives the development of all frameworks further and provides a rich set of
options to choose from.
D jango is one of the available frameworks for Python, so the question is: what sets
it apart to become the topic of this book, and what makes it popular in the Python
community? The next subsections will answer these questions by providing an
overview of the main advantages of Django.
Tight Integration between Components
First of all, Django provides a set of tightly integrated components; all of these
components have been developed by the Django team themselves. Django was
originally developed as an in-house framework for managing a series of news-oriented
websites. Later its code was released on the Internet and the Django team continued its
development using the Open Source model. Because of its roots, Django’s components
were designed for integration, reusability and speed from the start.
Django’s database component, the Object-Relational Mapper (ORM), provides a
bridge between the data model and the database engine. It supports a large set of
database systems, and switching from one engine to another is a matter of changing
a confi guration fi le. This gives the developer great fl exibility if a decision is made to
change from one database engine to another.
Clean URL Design
The URL system in Django is very flexible and powerful; it lets you defi ne patterns
for the URLs in your application, and defi ne Python functions to handle each pattern.
This enables developers to create URLs that are both user and search engine friendly.
Automatic Administration Interface
D jango comes with an administration interface that is ready to be used. This interface
makes the management of your application’s data a breeze. It is also highly flexible
Advanced Development Environment
I n addition, Django provides a very nice development environment. It comes with a
lightweight web server for development and testing. When the debugging mode is
enabled, Django provides very thorough and detailed error messages with a lot of
debugging information. All of this makes isolating and fi xing bugs very easy.
Django supports multi-lingual websites through its built-in internationalization
system. This can be very valuable for those working on websites with more than one
language. The system makes translating the interface a very simple task.
The standard features expected of a web framework are all available in Django.
These include the following:
- A template and text fi ltering engine with simple but extensible syntax.
- A form generation and validation API.
- An extensible authentication system.
- A caching system for speeding up the performance of applications.
- A feed framework for generating RSS feeds.
Ajax, choosing one and integrating it with Django is a straightforward matter, as we
will see in later chapters.
So to conclude, Django provides a set of integrated and mature components, with
excellent documentation, at http://www.djangoproject.com/documentation/,
thanks to its large community of developers and users. With Django available, there
has never been a better time to start learning a web development framework!
History of Django
Django started as an internal project at the Lawrence Journal-World newspaper in
2003. The web development team there often had to implement new features or even
entire applications within hours. Therefore, Django was created to meet the fast
deadlines of journalism websites, whilst at the same time keeping the development
process clean and maintainable. By the summer of 2005, Django became mature
enough to handle several high traffi c sites, and the developers decided to release it to
the public as an Open Source project. The project was named after the jazz guitarist
Now that Django is an Open Source project, it has gathered developers and users
from all over the world. Bug fi xes and new features are introduced on a daily basis,
while the original development team keeps an eye on the whole process to make sure
that Django remains what it is meant to be—a web framework for building clean,
maintainable and reusable web applications.
Web development has achieved large leaps of progress over the last few years. The
advent of scripting languages, web frameworks, and Ajax made rapid development
of web applications possible and easier than ever. This book takes you through a
tutorial for building a Web 2.0 application using two hot technologies—Python and
Django. The application allows users to store and share bookmarks. Many of the
exciting Web 2.0 applications will be explained and developed throughout this book.
In the next chapter, we will set up our development environment by installing the
necessary software, and get a feel for Django by creating our first application.
* Django shines when it comes to developing "content-oriented" web sites
* No programming language offers what Python does philosophically.
* Web Development Environment for Python Server Pages and Oracle