DjangoOpen Data NC Bo Warren Ben Parisi Austin Schneider Brian Bollerman

About● free and opensource web framework

○ BSD licenced● written in python

○ supports any platform that python supports● purpose: ease creation of database driven, complex websites

○ covers most aspects of web development (databases, views, controllers)

● Follows Don’t repeat yourself Principle○ “Every piece of knowledge must have a single, unambiguous,

authoritative representation within a system.”○ - The Pragmatic Programmer○ synchronized changes

History● began in 2003 at Lawrence Journal-World newspaper, Kansas

○ to help web developers create websites efficiently within a limited time period

● Initial release: 2005● named after guitarist Django Reinhardt● In 2008 Django Software Foundation founded and received 501(c)(3) non-

profit status○ gives out “awards” ○ foster community

Motivation● What does it fix?

○ 2 challenges:■ making data (stories, blog posts, etc) look presentable and

consistent■ intensive deadlines of a newsroom

○ writing straight html/css/javascript/php/sql■ lots of time■ complicated■ learning curve

Structure of the Framework

Source: http://www.erikmitchell.info/2010/09/28/using-django-to-create-complex-sites-simply/

URL Handling

•Idea: Create a python module that maps URL patterns (as

regular expressions) to Python functions (the desired views for

each URL)

URL Handling

•Django uses file urls.py and looks for variable “urlpatterns”

which is of datatype list

•Django runs through each URL pattern in order and stops at the

first one that matches.

URL Handling

•Once one of the regular expressions matches, Django imports

and calls the chosen view, which is a Python function, and passes

it an instance of an HttpRequest class (created by Django), as

well as the matched parts of the regular expression

Structure of the Framework

Structure of the Framework

View

● When a regular expression is matched in urls.py○ a function in views.py is

called.● The function returns a render

of an html page or a 404.

Templates● Text documents or python strings that are marked-up using

Django Template Language to generate text-based formats (HTML, XML, CSV, etc.)○ Block tags:

■ {% if is_logged_in %} logged in? {% else %} login {% endif %}

○ Variables:■ My dog’s name is {{ dogs_name }}.

Templates cont.

Templates cont.

Database Interaction● supported dbs

○ postgreSQL, mySQL, Sqlite, Oracle● doesn’t support non-relational

○ e.g. mongoDB● little/no sql needs to be written by developer● why no sql?

○ streamline● tables are python classes

○ used as an api, much easier○ to interact with db, all you have to do is import the classes

■ create new objects of type class, set and interact w/ standard methods

Demo: ● Create, Populate, & Query a DB

Sites using Django● https://www.pinterest.com/

● http://www.theonion.com/

● http://instagram.com/

● https://disqus.com/