Django Overview

(will add more soon...)

#1 Setup a basic Django project

, I've been getting more and more interested in Django. I think why shouldn't I write a series about it. So, let's start with the basics first: how to setup Django development environment and build a basic Django project.

1. Setup environments

• Install Python

       Get Python at http://www.python.org
       To verify if it's already installed, at console:
   $ python
   Python 2.6.6 (r266:84292, Sep 15 2010, 15:52:39) 
   [GCC 4.4.5] on linux2
   Type "help", "copyright", "credits" or "license" for more information.

• Install Django

       Download a Django release at http://www.djangoproject.com/download/
   $ tar xzvf Django.tar.gz
   $ cd Django
   $ sudo python setup.py install 

       To verfiy what's your current Django's version
   $ python
   >>> import django
   >>> django.get_version()
    
2. Create a basic Django project 

• To initialize project 

    $ django-admin.py startproject mysite
          This will create a basic Django project in mysite directory that looks as below
    mysite/
       __init__.py
       manage.py
       settings.py
       urls.py

• Now run a development webserver to see if your Django site works

    $ python manage.py runserver
    Validating models...
    0 errors found.

    Django version 1.0, using settings 'mysite.settings'
    Development server is running at http://127.0.0.1:8000/
    Quit the server with CONTROL-C.       

• Goto http://127.0.0.1:8000 on your Web browser, you'll see a "Welcome to Django" page. It's works!

So, you have setup a very basic Django project. If you want to make more complex stuffs, you may need to use a database backend, create some models, build your site's templates, mapping urls to what will process & response the corressponding templates (Django call this "views"), add some caching mechanisms to boost performance,...

How caching works in Django

Last time, I had a chance joining to a Django project. Django is a web framework written by Python. Though I've invested sometime before to study Django and been amazing with it, I haven't really done anything on Django yet. So that's a good opportunity for me to increase my Django knowledge. One of my tasks at start was to study caching supports in Django. Compare to what I knew with Ruby on Rails, I found that caching in Django is very strong and especially well-organized. So, it would be useful to put some summarizations down here.  

1. General rule
   
   
   given a URL, try finding that page in the cache
   if the page is in the cache:
       return the cached page
   else:
       generate the page
       save the generated page in the cache (for next time)
       return the generated page
   
   
2. More specific
   
   
   
   
3. Advantages and disadvantages of caching backends
   
   

   	Advantages	Disadvantages
   Memcached	- the fastest, most efficient type of cache available to Django - all cached data is stored directly in memory, so there’s no overhead of database or filesystem usage - cached data can be shared over multiple machines, so it’s excellent for scaling - being used by Facebook, Wikipedia,...	- cached data is stored in memory, so it will be lost if server crashes (but it’s not critical because cached data is just temporary) - need to have memcached daemon along the way
   In-database cached	- cached data is persistent - could use multiple databases for caching	- setup & manage multiple caching databases would be tough
   Filesystem cached	- cached data is persistent - simple to setup	- may not scale well
   Local-memory cached	- simple - not nescessary to have runing an external cache server as memcached	- no cross-process caching means it’s not particularly memory-efficient - probably not a good choice for production, just nice for development

   
   
4. Reference
   http://docs.djangoproject.com/en/1.2/topics/cache/