06. Backend

Now we will setup the backend so that we can start creating and updating Categories and Products by making requests to the API.

One thing that you should know is that you can create your backend in any directory, since this will be a complete separate server which we serve the data for our frontend application.

Now let's create a folder name back.

Creating .env

We will create virtual environment for our backend by following commands. Please make sure you create your backend in Linux or WSL(mac users can using bash terminal).

python3 -m venv .env
source .env/bin/activate

Installation

Please install the flask framework by running the following command:

pip install flask

Creating the app

Create a file name main.py and add the following code:

python filename=main.py

# --- Imports Start here--- ###
from flask import Flask
# --- Imports End here--- ###

app = None

# ---- Flask app factory ---- #


def create_app():
    app = Flask(__name__)
    return app


if __name__ == "__main__":
    app.run()

Starts the backend server by running the file main.py:

python3 main.py

For all the configurations of the application we create a separate file named config.py where will write all the configuration related with application.

Database Configuration

python filename=config.py

class LocalDevelopmentConfig:
    DEBUG = True
    SQLALCHEMY_DATABASE_URI = 'sqlite:///database.db'

You can see we have created a LocalDevelopmentConfig which will hold all the configuration related with local development.

Creating the database

After this configuration we will create the database and the tables to store data into the database.

Note We will SQlite database and in the model/table will start with usert table. Flask-SQLAlchemy will help us to all the operations ORM with database.

Flask-SQLAlchemy Installation

pip install flask-sqlalchemy

Creating the database

Create the database in a file named database.py.

python filename=database.py

from flask_sqlalchemy import SQLAlchemy

db = SQLAlchemy()

Now we will create the User table in a separate file named database.py:

python filename=models.py

class User(db.Model):
    __tablename__ = 'user'
    id = db.Column(db.Integer, primary_key=True, autoincrement=True)
    email = db.Column(db.String(100), unique=True)
    password = db.Column(db.String(100))
    name = db.Column(db.String(1000))
    role = db.Column(db.String)
    doj = db.Column(db.DateTime)
    loginAt = db.Column(db.DateTime)
    image = db.Column(db.BLOB)

See all the columns in the user table depends on your application's business logics. As a beginner, you can create any number of columns which you think required for your application.

Importing and Initializing the database

python filename=main.py

# --- Imports Start here--- ###
from flask import Flask
from database import db # [tl! add:start]
from models import (
    User
) # [tl! add:end]
# --- Imports End here--- ###

app = None

# ---- Flask app factory ---- #


def create_app():
    app = Flask(__name__)
    db.init_app(app) # [tl! add:start]
    app.app_context().push()
    db.create_all() # [tl! add:end]
    return app


if __name__ == "__main__":
    app.run()

Note > app_context is a function which is used to create and push an application context to make Flask's app-specific global variables (like current_app and g) accessible outside a request context.

db.create_all() method will create all the tables defined in the models.py file.

Testing it out

Now you can start the backend app using the following command.

python3 main.py

Let's commit the change using the following command.

git add .
git commit -m "database integrated"

Continue to start token-based-authentication...