2WeeksofDjango - A Django tutorial

Django provides a very nice ORM, which means you generally would not need to write database queries. IMO, Django’s well designed and very simple ORM is one of its strongest points. So lets dive in and start some code.

Before we start interacting with the database we need to tell Django the database connection details. This, and most other settings are defined in the file settings.py. For us that file is f:\project\settings.py. I am going to use the mySql database server, for no other reason than I already know this. You may want to use sqllite or PostgreSql.
Open the setting.py file and change the following lines to store the database details.

DATABASE_ENGINE = ‘mysql’ # ‘postgresql_psycopg2′, ‘postgresql’, ‘mysql’, ’sqlite3′ or ‘oracle’.
DATABASE_NAME = ‘dBlog’ # Or path to database file if using sqlite3.
DATABASE_USER = ‘user’ # Not used with sqlite3.
DATABASE_PASSWORD = ’secret’ # Not used with sqlite3.
DATABASE_HOST = ” # Set to empty string for localhost. Not used with sqlite3.
DATABASE_PORT = ” # Set to empty string for default. Not used with sqlite3.

You would have need to created the user and the database, using the tool provided by your database engine. Django can not do this for you.

The admin system provided with Django lets you do most of the basic CRUD without writing a line of code. So lets use that to see our data. We need to tell Django that we plan to use the admin functionality. Modify the settings.py to do this.

INSTALLED_APPS = (
‘django.contrib.auth’,
‘django.contrib.contenttypes’,
‘django.contrib.sessions’,
‘django.contrib.sites’,
‘django.contrib.admin’,
‘project.dBlog’
)

Basically we added ‘django.contrib.admin’ and ‘project.dBlog’ to INSTALLED_APPS.

Right now we just want to have blog posts and comment on them. Edit your models.py to create a table for blog entries and another for comments. Put the following code in models.py

from django.db import models
from django.contrib.auth.models import User

class Comment(models.Model):
comment_text = models.TextField(maxlength = 1000)
created_on = models.DateTimeField(auto_now_add = 1)
created_by = models.ForeignKey(User, unique = True)
comment_for = models.ForeignKey(Blog)
class Admin:
pass

Lets see what the code does.
The first line imports the module which contains django ORM. The next import imports User class which we would be using as we do not want to re write the authentication system. We have two classes Blog and Comment each corresponding to a database table. Such classes need to extend models.Model which we have done. We want the Blog table to contain some text, so we have entry, we want to keep track of when it was created, so we have created_on. created_by is a Foreign key to the User table, defined in django.contrib.auth.models . For each of them we have added a few attributes such as maxlength.

The code

class Admin:
pass

tell django that we want to modify these tables from the auto generated admin interface. Similarly we write the needed columns for Comment and give it a foreign key to Blog. (created_by = models.ForeignKey(User, unique = True))

Running the command manage.py syncdb would create the tables our application needs.

F:\project>manage.py syncdb
Creating table auth_message
Creating table auth_group
Creating table auth_user
Creating table auth_permission
Creating table django_content_type
Creating table django_session
Creating table django_site
Creating table django_admin_log
Creating table dBlog_blog
Creating table dBlog_comment
You just installed Django’s auth system, which means you don’t have any superuse
rs defined.
Would you like to create one now? (yes/no): yes
Username: shabda
E-mail address: shabda.raaj@gmail.com
Password:
Password (again):
Superuser created successfully.
Installing index for auth.Message model
Installing index for auth.Permission model
Installing index for admin.LogEntry model
Installing index for dBlog.Blog model
Installing index for dBlog.Comment model
Loading ‘initial_data’ fixtures…
No fixtures found.


We would be using Django’s authentication system, as declared in INSTALLED_APPS in setting.py, with the lines ‘django.contrib.auth’. So syncdb created a few tables for the authentication system and asked you to create a superuser.

To make the admin interface available we need to add

(r’^admin/’, include(’django.contrib.admin.urls’)),
to urls.py.

Now point your browser to localhost:8000/admin and you would be asked to log in. Log in using the user you created. You should see a screen like this .
Rejoice, our first app is almost ready.