Web3 backend and smart contract development for Python developers Musical NFTs part 3: Postgres database

Installing postgres database

Postgres installation procedure is written for WLS environment and it will presume that you already have WSL installed on your machine. If that's not the case go first to WSL documentation. (If you want to check if you have WSL already installed just can go to windows command line and type wsl -l -v). ALternativ is to install for you Windows machine (instruction you can find on official postgres documentation)

Installation from WSL terminal

$ sudo sh -c 'echo "deb http://apt.postgresql.org/pub/repos/apt $(lsb_release -cs)-pgdg main" > /etc/apt/sources.list.d/pgdg.list'

$ wget --quiet -O - https://www.postgresql.org/media/keys/ACCC4CF8.asc | sudo apt-key add -

$ sudo apt-get update

$ sudo apt-get -y install postgresql postgresql-contrib

$ psql --version
psql (PostgreSQL) 15.2 (Ubuntu 15.2-1.pgdg22.04+1)

$ sudo service postgresql status
15/main (port 5432): down

#starting server 
$ sudo service postgresql start
 * Starting PostgreSQL 15 database server

Starting new Django project and adding postgres to our settings.py file

Let's first install Django from virtual environment

$ pip install django
# update requirments
$ pip freeze > requirements.txt

This will install latest Django stabile version and add Django to our requirements.txt

To check if everything went well type

$python -m django --version
4.2.5

Now we will create new project in root directory musical_nft_thumbnails

$django-admin startproject musical_nft .

Now project root folder should look something like this:

├── env
├── manage.py
├── musical_nft
└── requirements.txt

In attempt to test Django and if everything worked as expected we should

$python manage.py runserver

If everything goes well we should see something like

Watching for file changes with StatReloader
Performing system checks...

System check identified no issues (0 silenced).

You have 18 unapplied migration(s). Your project may not work properly until you apply the migrations for app(s): admin, auth, contenttypes, sessions.
Run 'python manage.py migrate' to apply them.
September 21, 2023 - 20:03:07
Django version 4.2.5, using settings 'musical_nft.settings'
Starting development server at http://127.0.0.1:8000/
Quit the server with CONTROL-C.

Creatig user and new database

# Start server
$sudo service postgresql start
* Starting PostgreSQL 15 database server [ OK ] 
* Starting PostgreSQL 9.1 database server 

# now lets go to postgres command line and create user with password and give premisions to newly created user  
$sudo -u postgres psql
psql (15.4 (Ubuntu 15.4-1.pgdg20.04+1))
Type "help" for help.

# create database
postgres=#create database musical_nfts;

# create user
postgres=# create user denisdb with encrypted password 'testpassword';

# grant all privileges to newly created database to user denisdb
postgres=# grant all privileges on database musical_nfts to denisdb;

# change database ownership to avoid problem when executing migratations in Django 
postgres=# ALTER DATABASE musical_nfts OWNER TO denisdb;

Exit postgres comand line and install Python package psycopg2 (Psycopg is the most popular PostgreSQL database adapter for the Python programming language)

$pip install psycopg2
$pip freeze > requirements.txt

Before we move to settings.py let's install django-environ library for
managing environment variables in our project.

$pip install django-environ
$pip freeze > requirements.txt

In root folder create file .env and write inside:

DENIS_PASS=testpassword

Add .env to our .gitignore file.

env/
.env

Inside musical_nft folder you should now be able to find and open settings.py

On the top of Django settings.py file, above security variable you can pass:

from pathlib import Path
import os
import environ

# Build paths inside the project like this: BASE_DIR / 'subdir'.
BASE_DIR = Path(__file__).resolve().parent.parent


env = environ.Env()
env_file = os.path.join(BASE_DIR, ".env")
if os.path.isfile(env_file):
    # read a local .env file
    env.read_env(env_file)
    password = env("DENIS_PASS")
else:
    raise ValueError("We cannot find .env file")

SECRET_KEY = "django-insecure-#!!l7=be79=9h#ng$+l4mgxp$p6n7^boxvqnd!(x8vxx)##+4m"

Then over database setting inside Django settings.py you can pass

DATABASES = {
"default": {
    "ENGINE": "django.db.backends.postgresql",
    "NAME": "musical_nfts",
    "USER": "denisdb",
    "PASSWORD": password,
    "HOST": "localhost",
    "PORT": "",
}

}

When you run your Django you should see something like this

$python manage.py runserver
Watching for file changes with StatReloader
Performing system checks...

System check identified no issues (0 silenced).

You have 18 unapplied migration(s). Your project may not work properly until you apply the migrations for app(s): admin, auth, contenttypes, sessions.
Run 'python manage.py migrate' to apply them.
September 22, 2023 - 00:41:37
Django version 4.2.5, using settings 'musical_nft.settings'
Starting development server at http://127.0.0.1:8000/
Quit the server with CONTROL-C.

Django comes with some pre-coded models that we need to migrate even if we didn't add neither one app model. That is why now is time to make Django migrations and to erase error we got above:
You have 18 unapplied migration(s). Your project may not work properly until you apply the migrations for app(s): admin, auth, contenttypes, sessions.
Run 'python manage.py migrate' to apply them.


$python manage.py makemigrations
$python manage.py migrate

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 admin.0002_logentry_remove_auto_add... OK
Applying admin.0003_logentry_add_action_flag_choices... OK
Applying contenttypes.0002_remove_content_type_name... OK
Applying auth.0002_alter_permission_name_max_length... OK
Applying auth.0003_alter_user_email_max_length... OK
Applying auth.0004_alter_user_username_opts... OK
Applying auth.0005_alter_user_last_login_null... OK
Applying auth.0006_require_contenttypes_0002... OK
Applying auth.0007_alter_validators_add_error_messages... OK
Applying auth.0008_alter_user_username_max_length... OK
Applying auth.0009_alter_user_last_name_max_length... OK
Applying auth.0010_alter_group_name_max_length... OK
Applying auth.0011_update_proxy_permissions... OK
Applying auth.0012_alter_user_first_name_max_length... OK
Applying sessions.0001_initial... OK

At this point we can start to build our web3 backend.

Code you can found in github repo