How To Create Web Application using Django-Part I

Creating Web Application with Django

Django is an open source web framework that helps to create a Web Applications. It is a high-level Python Web framework which encourages rapid development and clean, pragmatic design. In this tutorial we will learn how to create Web Applications using Django.

For installation of Django

visit https://www.linuxhelp.com/how-to-install-and-configure-django-in-centosdebian/

To Create a new web application using Django

When you create an app, Django automatically sets up a ' Sqlite' database which is used to store data for the web applications.
Move to the project directory and execute ' python manage.py' after activating the virtual environment.

(myproject)root@linuxhelp:~# ls
Desktop Documents examples.desktop Pictures Templates
django Downloads Music Public Videos
(myproject)root@linuxhelp:~# cd django/
(myproject)root@linuxhelp:~/django# ls
myproject sampleproject
(myproject)root@linuxhelp:~/django# cd sampleproject/
(myproject)root@linuxhelp:~/django/sampleproject# ls
db.sqlite3 manage.py sampleproject
(myproject)root@linuxhelp:~/django/sampleproject# python manage.py startapp myapp

A new application ' myapp' will be created under your current directory. Lets view the files inside the directory.

(myproject)root@linuxhelp:~/django/sampleproject# ls
db.sqlite3 manage.py myapp sampleproject
(myproject)root@linuxhelp:~/django/sampleproject# ls myapp
admin.py apps.py __init__.py migrations models.py tests.py views.py

Move to the sample project directory and select the file ' settings.py' .

(myproject)root@linuxhelp:~/django/sampleproject# cd sampleproject/
(myproject)root@linuxhelp:~/django/sampleproject/sampleproject# ls
__init__.py settings.py urls.py wsgi.py
__init__.pyc settings.pyc urls.pyc wsgi.pyc
(myproject)root@linuxhelp:~/django/sampleproject/sampleproject# vim settings.py

Check the INSTALLED_APPS section and add myapp inside single quotes as shown below.

INSTALLED_APPS = (
' django.contrib.admin' ,
' django.contrib.auth' ,
' django.contrib.contenttypes' ,
' django.contrib.sessions' ,
' django.contrib.messages' ,
' django.contrib.staticfiles' ,
' myapp' 
)

Now ' myapp' will be activated with the other built-in applications in the Django instance.

Importing Django models into our Project

After creating the application directory ' myapp' , import the pre-defined models of python into ' models.py' and define the objects of the application.

(myproject)root@linuxhelp:~/django/sampleproject/sampleproject# cd ..
(myproject)root@linuxhelp:~/django/sampleproject# ls
db.sqlite3 manage.py myapp sampleproject
(myproject)root@linuxhelp:~/django/sampleproject# cd myapp
(myproject)root@linuxhelp:~/django/sampleproject/myapp# ls
admin.py apps.py __init__.py migrations models.py tests.py views.py
(myproject)root@linuxhelp:~/django/sampleproject/myapp# vim models.py

' models.py' file appears as below.

Entry:
from django.db import models
class Person(models.Model):
name = models.CharField(max_length=50)
class Group(models.Model):
name = models.CharField(max_length=128)
members = models.ManyToManyField(Person, through=' Membership' , through_fields=(' group' , ' person' ))
class Membership(models.Model):
group = models.ForeignKey(Group)
person = models.ForeignKey(Person)
inviter = models.ForeignKey(Person, related_name=" membership_invites" )
invite_reason = models.CharField(max_length=64)

Explanation
1. Lines starting with the from keyword indicate that we are importing modules from an existing file or library, here it is located inside /root/django/myproject/lib/python2.7/site-packages/django/db and utils, respectively.
2. Each model is defined via a class that derived from django.db.models.
3. We are importing the following models Person, Group and Membership from the django.db file.

Creating Django Database

The models should be migrated to the database to store the data created inside each models. If you make changes to your model later, you have to repeat this step.

(myproject)root@linuxhelp:~/django/sampleproject# python manage.py makemigrations myapp
Migrations for ' myapp' :
0001_initial.py:
- Create model Group
- Create model Membership
- Create model Person
- Add field inviter to membership
- Add field person to membership
- Add field members to group
(myproject)root@linuxhelp:~/django/sampleproject# python manage.py migrate myappOperations to perform:
Apply all migrations: myapp
Running migrations:
Rendering model states... DONE
Applying myapp.0001_initial... OK

(myproject)root@linuxhelp:~/django/sampleproject# python manage.py createsuperuser
Username (leave blank to use ' root' ): linuxhelp
Email address:
Password:
Password (again):
Superuser created successfully.

(myproject)root@linuxhelp:~/django/sampleproject# ls
db.sqlite3 manage.py myapp sampleproject
(myproject)root@linuxhelp:~/django/sampleproject# cd myapp
admin.py apps.py __init__.pyc models.py tests.py
admin.pyc __init__.py migrations models.pyc views.py
(myproject)root@linuxhelp:~/django/sampleproject/myapp# vim admin.py

Entry:
from django.contrib import admin
from .models import Person
from .models import Group
from .models import Membership
# Register your models here.
admin.site.register(Person)
admin.site.register(Group)
admin.site.register(Membership)

(myproject)root@linuxhelp:~/django/sampleproject# python manage.py runserver 0.0.0.0:8000
Performing system checks...
System check identified no issues (0 silenced).
April 28, 2016 - 12:22:08
Django version 1.9.5, using settings ' sampleproject.settings' 
Starting development server at http://0.0.0.0:8000/
Quit the server with CONTROL-C.