Let us create a Python application for "online poll" based on Django. The first thing you should do is changing your working directory to your project.

$ cd my_project


STEP 1. Create an application

In order to create an app, you will need "manage.py" created by Django. Once you verify it, you can create "online poll" app by running below command.

$ python manage.py startapp polls


You will be able to see the directory structure like below if you haven't faced any error

polls/
    __init__.py
    admin.py
    apps.py
    migrations/
        __init__.py
    models.py
    tests.py
    views.py

So above directory will be your base camp for "online poll" application.

Creating a first view

Let us open views.py and add some codes like below.

from django.shortcuts import render

# Create your views here.
from django.http import HttpResponse


def index(request):
    return HttpResponse("Hello, world. You're at the polls index.")

The above is the most simple example of view in Django. In order to call view, you should use URLconf in order to have the connected URL. What you should do is just creating a null file as urls.py. You can do it like below

$ touch urls.py

Then you should be able to see your directory structure like below

polls/
    __init__.py
    admin.py
    apps.py
    migrations/
        __init__.py
    models.py
    tests.py
    urls.py
    views.py

And let us put below content to urls.py

from django.urls import path

from . import views

urlpatterns = [
    path('', views.index, name='index'),
]

The next action you should do is adding following two lines to url.py on your project like below.

from django.conf.urls import include


path('polls/', include('polls.urls')),

So, the final code should be like below

from django.contrib import admin
from django.urls import include, path
from django.conf.urls import include


urlpatterns = [
    path('admin/', admin.site.urls),
    path('polls/', include('polls.urls')),
]

Now index view is integrated with URLconf. Time for you to check your server by following command like

$ python manage.py runserver

If you face an error like below, you should check if your python is properly installed and django is running on virtual environment like I mentioned at "1. How do I setup Django development environment on Mac?" or not.


STEP 2. Database setup

If everything goes fine, now is time for us to setup a database where can store poll results. Let us do it step by step.

  1. Open up settings.py on your project, and you can see the default database setting like below

    # Database
# https://docs.djangoproject.com/en/2.1/ref/settings/#databases


DATABASES = {
    'default': {
        'ENGINE': 'django.db.backends.sqlite3',
        'NAME': os.path.join(BASE_DIR, 'db.sqlite3'),
    }
}

    If you want to use mysql instead of sqlite3, you can use it by replacing as "django.db.backends.mysql". For oracle, it will be "django.db.backends.oracle". 
    If you are not using SQLite as your database, additional settings such as USER, PASSWORD, and HOST must be added. For more details, see the reference documentation for DATABASES.
    Example)

    DATABASES = {
    'default': {
        'ENGINE': 'django.db.backends.postgresql',
        'USER': 'mydatabaseuser',
        'NAME': 'mydatabase',
        'TEST': {
            'NAME': 'mytestdatabase',
        },
    },
}


    Once you set all your requirements, you should run following command.


    python manage.py migrate





  2. Creating models for online poll.

    In our simple poll app, we’ll create two models: Question and Choice. A Question has a question and a publication date. A Choice has two fields: the text of the choice and a vote tally. Each Choice is associated with a Question.

    These concepts are represented by simple Python classes. Edit the polls/models.py file so it looks like this:

    from django.db import models

# Create your models here.

class Question(models.Model):
    question_text = models.CharField(max_length=200)
    pub_date = models.DateTimeField('date published')

class Choice(models.Model):
    question = models.ForeignKey(Question, on_delete=models.CASCADE)
    choice_text = models.CharField(max_length=200)
    votes = models.IntegerField(default=0)

    If you see above, it looks like a table schema when we create a table in database. I won't elaborate the detail about above for this time.

  3. Activating models
    Even though we have created an app at the moment, but actually we can't say "polls" are correctly integrated with the project. In django, we should make some additional action to make it happen.
    To include the app in our project, we need to add a reference to its configuration class in the INSTALLED_APPS setting. The PollsConfig class is in the polls/apps.py file,

    from django.apps import AppConfig

class PollsConfig(AppConfig):
    name = 'polls'


    so its dotted path is 'polls.apps.PollsConfig'. Edit the <your project folder>/settings.py file and add that dotted path to the INSTALLED_APPS setting. It’ll look like this:

    INSTALLED_APPS = [
    'polls.apps.PollsConfig',
    'django.contrib.admin',
    'django.contrib.auth',
    'django.contrib.contenttypes',
    'django.contrib.sessions',
    'django.contrib.messages',
    'django.contrib.staticfiles',
]