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Creating a Django App Using PostgreSQL Database

January 12, 2021

Django is a high-level Python Web framework that encourages rapid development, clean, and pragmatic design. Built by experienced developers, it takes care of much of the hassle of web development, so you can focus on writing your app without needing to reinvent the wheel. Best of all, it’s free and open-source.

PostgreSQL is a powerful, open-source object-relational database system that uses and extends the SQL language combined with many features that safely store and scale the most complicated data workloads.

Prerequisites

To follow along with this tutorial, you should have:

Step 1: Creating our database through the command line

Open the PostgreSQL shell. You can find the PSQL Shell in the Start Menu.

access psql

The shell will prompt you for Server, Database, Port, and Username details. You can set it to default by clicking on the Enter button in the keyboard without providing any value. Finally, the shell will prompt you for the Password.

You should provide the password that you used during the PostgreSQL installation. You will see a similar result in your PSQL shell like the one the above image if correctly implemented.

psql_shell

Let’s create a PostgreSQL database.

The CREATE DATABASE command let’s us create a new database in PostgreSQL.

CREATE DATABASE helloworld;

The CREATE USER command let’s us create a user for our database along with a password.

CREATE USER <yourname> WITH PASSWORD '<password>';

Let’s modify a few connection parameters for the new database user.

ALTER ROLE <yourname> SET client_encoding TO 'utf8';
ALTER ROLE <yourname> SET default_transaction_isolation TO 'read committed';
ALTER ROLE <yourname> SET timezone TO 'UTC';

  • In the first line we are setting the default encoding to UTF-8 expected by Django.

  • With the second line we are also setting the default transaction isolation scheme to “read committed”, that blocks reads from uncommitted transactions.

  • Finally, by default Django timezone is UTC we are setting our database’s timezone to UTC.

Next, we have to grant our new user access to the database we created earlier.

GRANT ALL PRIVILEGES ON DATABASE helloworld TO <yourname>;

Step 2: Creating a virtual environment & installing necessary Python packages

Let’s start by creating a folder for our project.

 mkdir myproject   #creating our project folder
 cd myproject     #changing into our project folder directory

A virtual environment helps create an isolated Python environment that will contain all that packages that our Django project will need. Let’s create a virtual environment named venv.

virtualenv venv

When we activate our virtual environment, any Python packages installed will only be available for our Django project.

To activate the venv virtual environment, run:

source venv/bin/activate

pip is the standard package manager for Python. pip is used to install Python packages from the Python package index(PyPI). More on pip here.

Let’s install django and psycopg2 using pip. psycopg2 is a popular PostgreSQL database adapter for Python.

pip install django psycopg2

Let’s create our Hello World Django project.

 django-admin startproject django_app

Change your current directory into our Django project django_app.

cd django_app

Let’s create an hello_world app in our django_app project.

A Django application is a Python package that is specifically intended for use in a Django project. Django apps are reusable in different Django project.

django-admin startapp hello_world

For our hello_world app to work we need to register the app in the django_app project. To do this, let’s navigate to the django_app/settings.py.

Add the hello_world app name to the installed apps section of the file.

...
INSTALLED_APPS = [
    ...
    'django.contrib.messages',
    'django.contrib.staticfiles',
    'hello_world',  # registering the hello_world app
]

Step 3: Set up your project to use PostgreSQL database

SQlite is the default database that comes with Django. We need to change the database configurations to use PostgreSQL.

Let’s navigate to django_app/settings.py. In the DATABASES section, you’ll see the code snippet below.

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

Change the above code snippet to this:

DATABASES = {
    'default': {
        'ENGINE': 'django.db.backends.postgresql_psycopg2',
        'NAME': 'helloworld',
        'USER': '<yourname>',
        'PASSWORD': 'password',
        'HOST': 'localhost',
        'PORT': '',
    }
}

We changed the database engine to use postgresql_psycopg2 instead of the default sqlite3.

  • NAME is the name of the database we created for our project.

  • USER is the database user we created during the database creation.

  • PASSWORD is the password to the database we created.

Now, let’s make sure that we have connected to the PostgreSQL database.

The manage.py file is a Python script that allows us to perform adminstartive tasks like migrations, running the server, etc.

The makemigrations command is responsible for creating new migrations based on the changes you have made to our models. Since we don’t have a model in our Django project, we will not worry about this.

python manage.py makemigrations

When you run it for the first time, the default models in the Django project will get migrated and the makemigrations command creates a file with all the SQL commands that needs to be executed for the models. The migrate command will execute SQL commands.

python manage.py migrate

After running the above command, you will get something like this in your CLI.

Operations to perform:
  Apply all migrations: admin, auth, contenttypes, sessions
Running migrations:
  Applying contenttypes.0001_initial... OK
  Applying auth.0001_initial... OK
  Applying admin.0001_initial... OK
  ....
  ....
  Applying auth.0012_alter_user_first_name_max_length... OK
  Applying sessions.0001_initial... OK

python manage.py migrate command created some default tables in our database.

postgres_database.

To get a better understanding of what this command does, check out this article Django Migrations: A Primer.

Now, Let’s start the server by running this command:

python manage.py runserver

After running the command above, proceed to visit http://127.0.0.1:8000 in your browser.

If your Django project runs without any errors, you should see something like this.

Django Homepage

Congratulations! you’ve configured Django to use PostgresSQL.

Hello World In Django

First, let create a templates folder in our django_app/templates directory and create an index.html file. Your project directory should look like this.

--django_app
| ---django_app
| ---hello_world
| ---templates
|     --- index.html
| ---manage.py

The templates folder is the display layer that handles user interface of our Django project. It contains HTML, CSS, and JavaScript files that are required in our Django project. We can use a single template folder for our entire project, or we can create different templates folder for each app in our Django project. Since we only have one app, which is our helloworld app, we will stick to using a single template folder for our project.

Django web framework comes with is own built-in template engine called the Django template language. For more information on Django template langauage.

Let’s configure our app to make use of the templates folder. Head over to django_app/settings.py the TEMPLATES section.

TEMPLATES = [
   {
       'BACKEND': 'django.template.backends.django.DjangoTemplates',
       'DIRS': [
           Path(BASE_DIR, 'templates') #include this line to your file
       ],
       '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',
           ],
       },
   },
]

In hello_world/views.py, add the homepage() function, that will render our index.html file.

from django.shortcuts import render

def homepage(request):
  return render(request, 'index.html', context={})

Let’s create a new Python file in the hello_world folder, hello_world/urls.py.

from django.urls import path
from . import views  #importing our view file 

urlpatterns = [
    path("", views.homepage, name="home"), #mapping the homepage function
]

Now, let’s map the hello_world/urls.py file to /. In django_app/urls.py:

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

urlpatterns = [
    path('admin/', admin.site.urls),
    path("", include("hello_world.urls")),  # add this line
]

The above code in our django_app/urls.py file maps the available URLs in the hello_world/urls.py to /.

For more information on views and URLs in Django, refer here.

Let’s navigate to the index.html in our templates folder and add this:

<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Hello World App</title>
</head>
<body>
    <h1> Hello World </h1>
</body>
</html>

If the development server is still running visit http://127.0.0.1:8000 in your browser or run the python manage.py runserver command again.

homepage

If you can see the image above, Congratulations! You just created a Hello World App in Django.

References

  1. Django.

  2. PostgreSQL.

  3. Views and URLs in Django.

  4. Django Migrations.

Peer Review Contributions by: Mohan Raj