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GNHLUG Web>PySIGDjango20070222 (2007-02-26, TedRoche) (raw view)
PySIG Django Presentation   -   Feb. 22, 2007

Dave Rowell, Appropriate Solutions, Inc., Peterborough, NH
drowell@appropriatesolutions.com

Definition of Django

From the Django site: "Django is a high-level Python Web framework that encourages rapid development and clean, pragmatic design."

Supporting examples:
   * Simple (for a programmer) to set up and get going.
   * Uses and allows loosely coupled components.
   * Encourages well-formed urls.
   * MVC-ish design separates data, business logic and appearance: Model (data design), View (business logic), Template (presentation).

Why I like Django

Good use of Python. Except for the templates, the components you work with are all Python code.

The framework is high-level with lots of useful components, but it's also flexible with hooks to get in and do whatever you need to do. However, more and more I find that when I need to do something,
someone's already done it and left me well-designed tools to do the same.

What Appropriate Solutions uses Django for

* Site to display current and historical credit exchange rates. It was my first Django app and also complex enough to make Django's automatic admin interface uncomfortable. I think I'd like to come back to this app after more experience and see if I can make it fit better. This app required writing several largish SQL queries.

* An internal hour-tracking application (in development).

* Low-cost e-commerice web sites. A good fit for Django. I actually found myself removing code and files as I learned to use the built-in Django tools. As our web store app becomes more complicated, we may consider converting to Satchmo, a Django-based e-commerce project with more complicated features (www.satchmoproject.com).

Django features

From "Django for Non-Programmers" (link below):

   * Administrative interface (for adding/deleting/modifying items in the database)
   * Database connectivity (several supported databases – PostgreSQL, MySQL, Oracle in the works - no SQL needed)
   * Authentication and authorization (users, groups, and permissions)
   * URL configuration (for making simple, clean URLs)
   * Internationalization (makes localization easy)   
   * Feed syndication (RSS/Atom)
   * Comments on any type of object (both anonymous comments, which Django calls “free comments” and comments that require registration)
   * Flat pages (simple HTML content stored in the database and passed into a template)

Also (from my programmer perspective):
   * Builds your database for you from your model classes (models.py)
   * Development web server that works as you modify code and provides debug information
   * Supports scalable hosting (Apache with ModPython, lighttpd)
   * Many content caching options
   * Projects can consist of several pluggable applications
   * Generic views that handle common data models (category/item, date archive)
   * Extensible template language

The basic Django app components

settings.py - general control over environment and what's included in your web project

models.py - defines your data model - from this Django will build a complete DB schema

urls.py - regular expressions that map URLs to views views.py - Python programs that build the data context of a web page and choose the template to display it

templates – html page templates with {{ variables }} and {% block tags %} that provide display logic (loops, if-then)

Django Links

   * Main Django site, the official Django reference, http://www.djangoproject.com/

   * The Django Book, an on-line book in progress, http://www.djangobook.com/en/beta/

   * James Bennet's (Django developer) enlightening blog entries on Django,
http://www.b-list.org/feeds/categories/django

   * Django for Non-Programmers, Django web designer's (Jeff Croft, World
Online) point of view, http://www2.jeffcroft.com/blog/2006/may/02/django-non-programmers/

   * Django Sites List, a list of sites that use Django, http://code.djangoproject.com/wiki/DjangoPoweredSites
Topic revision: r1 - 2007-02-26 - TedRoche
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