Addition Using Django

PIP installation steps

First, we need to install the pip package manager.
pip is a package management system used to install and manage software packages written in Python.
For python version 2.7.X use
anurag@anurag:~$ sudo apt-get install python-pip
For python version 3.X use
anurag@anurag:~$ sudo apt-get install python3-pip
Once you have installed pip, you are ready to install Django on your system.

Django installation steps

Pip will install the latest Django version available in pip repository
Python 2.7.X
sudo pip install django
Python 3.X
sudo pip3 install django
You can verify Django installation by typing:
anurag@anurag:~$ django-admin --version

Description of project

We are creating a sample web page for addition of two numbers using Django
Django: Django is a free and open-source web framework, written in Python, which follows the model-view-template architectural pattern.
The developer provides the Model, the view and the template then just maps it to a URL and Django does the magic to serve it to the user

Flow of a Django project

Addition project

Creating a Django Project

anurag@anurag:~$ django-admin startproject addition This command will create directory named addition

addition 
├───manage.py
└───addition
        settings.py
        urls.py
        wsgi.py
        __init__.py

init.py − Just to make sure python handles this folder as a package.
admin.py − This file helps you make the app modifiable in the admin interface.
models.py − This is where all the application models are stored.
views.py − This is where your application views are.

Starting a web server

To start a web server you need to be in the project directory and run the following command
anurag@anurag:~/addition$ python manage.py runserver 0.0.0.0:8000 You will get the following message

February 02, 2017 - 03:00:35
Django version 1.10.5, using settings 'sampleproject.settings'
Starting development server at http://127.0.0.1:8000/
Quit the server with CONTROL-C.

Now all you need to do is check that your website is running. Open your browser (Firefox, Chrome, Safari, Internet Explorer or whatever you use) and enter this address:
http://127.0.0.1:8000

Views

A view is a “type” of Web page in your Django application that generally serves a specific function and has a specific template. A view function, or “view” for short, is simply a Python function that takes a web request and returns a web response. This response can be the HTML contents of a Web page, or a redirect, or a 404 error, or an XML document, or an image, etc. Example: You use view to create web pages, note that you need to associate a view to a URL to see it as a web page. In django views are created in views.py file. Here, we have defined a view hello In in function hello(request) we are additing two number 10 and 19 and rendering hello.html to display addition at "http://127.0.0.1:8000/hello" we will get to this part in Urls section

from django.shortcuts import render
def hello(request):
   a = 10
   b = 19
   return render(request, "hello.html", {"result": a + b})

Templates

All of your html files will be in addition/template. You need to create your own template directory by
anurag@anurag:~/addition$ mkdir template

addition 
├───manage.py
└───template
       hello.html

Now create a hello.html file template directory

<html>

  <body>
     Hello World!!!<p>Addition of 10+19 is {{result}}</p>
  </body>

</html>

Now we have to edit our settings.py file, so that python knows where all of our html files reside.
In settings.py, search for TEMPLATES which looks like this

TEMPLATES = [
   {
       'BACKEND': 'django.template.backends.django.DjangoTemplates',
       'DIRS': [''], 
       'APP_DIRS': True,
       'OPTIONS': {
           'context_processors': [
               'django.template.context_processors.debug',
               'django.template.context_processors.request',
               'django.contrib.auth.context_processors.auth',
               'django.contrib.messages.context_processors.messages',
           ],
       },
   },
]

Change it to

TEMPLATES = [
    {
        'BACKEND': 'django.template.backends.django.DjangoTemplates',
        'DIRS': ['template'], # <- name of our template directory
        'APP_DIRS': True,
        'OPTIONS': {
            'context_processors': [
                'django.template.context_processors.debug',
                'django.template.context_processors.request',
                'django.contrib.auth.context_processors.auth',
                'django.contrib.messages.context_processors.messages',
            ],
        },
    },
]

Urls

We want to access our view hello via a URL, first we need to associate that view with a URL. Django has his own way for URL mapping and it's done by editing your project url.py file (addition/url.py). First we need to import views hello from our views.py file Which looks like this:

from views import addition,hello
urlpatterns = [
    url(r'^admin/', admin.site.urls),
    url(r'^', hello, name = 'hello'),
]

Now that you have added a url for view addition you can access it at this url http://127.0.0.1:8000/hello Restart the server using
anurag@anurag:~/addition$ python manage.py runserver 0.0.0.0:8000 url(r'^', hello, name = 'hello') This line means that for every URL that starts with hello/, Django will find a corresponding view.

Models

A model is a class that represents table or collection in our DB, and where every attribute of the class is a field of the table or collection. Models are defined in the app/models.py (in our example: addition/models.py)

from django.db import models


class Numbers(models.Model):
    number1 = models.IntegerField()
    number2 = models.IntegerField()

    def __unicode__(self):
        return self.number1 + self.number2

Our class has 2 attribute number1 and number2 which are IntegerField, those will be the table fields.

Creating forms using models

class Numbers(forms.Form):
    class Meta:
        model = models.Numbers
        fields = ['number1', 'number2']

    number1 = forms.IntegerField()
    number2 = forms.IntegerField()

references links

Django Urls Django Views

a9raag/djangoaddition