DEV Community

Cover image for Python CRUD Rest API using Flask, SQLAlchemy, Postgres, Docker, Docker Compose
Francesco Ciulla
Francesco Ciulla

Posted on

Python CRUD Rest API using Flask, SQLAlchemy, Postgres, Docker, Docker Compose

#python #docker #postgres #beginners

Let's create a CRUD Rest API in Python, using the following:

  • Flask (Python web framework)
  • SQLAlchemy (ORM)
  • Postgres (database)
  • Docker (containerization)
  • Docker Compose (to run the application and the database in containers)

If you prefer a video version:

All the code is available in the GitHub repository (link in the video description): https://youtube.com/live/fHQWTsWqBdE

🏁 Intro

Here is a schema of the architecture of the application we are going to create:

crud, read, update, delete, to a flask app and postgres service, connected with docker compose. Postman and tableplus to test it

We will create 5 endpoints for basic CRUD operations:

  • Create
  • Read all
  • Read one
  • Update
  • Delete

Here are the steps we are going through:

  1. Create a Flask application using SQLALchemy as an ORM.
  2. Dockerize the Flask application writing a Dockerfile and a docker-compose.yml file to run the application and the database
  3. Run the Postgres database in a container using Docker Compose, and test it with TablePlus
  4. Run the Flask application in a container using Docker Compose, and test it with Postman

We will go with a step-by-step guide, so you can follow along.

🏁 Create a Flask application using SQLALchemy as an ORM

Create a new folder:

mkdir flask-crud-api
Enter fullscreen mode Exit fullscreen mode

step into the folder:

cd flask-crud-api
Enter fullscreen mode Exit fullscreen mode

Open the folder with your favorite IDE. I am using VSCode, so I will use the command:

code .
Enter fullscreen mode Exit fullscreen mode

We need just 4 files for the Flask application, including containerization.

You can create these files in different ways. One of them is to create them manually, the other one is to create them with the command line:

touch requirements.txt app.py Dockerfile docker-compose.yml
Enter fullscreen mode Exit fullscreen mode

Your folder structure should look like this:

folder structure - Build a CRUD Rest API in Python using Flask, SQLAlchemy, Postgres, Docker

🗒️requirements.txt file



The requirements.txt file contains all the dependencies of the project. In our case we will need just 3.

Let's add them to the requirements.txt file:

flask
psycopg2-binary
Flask-SQLAlchemy
Enter fullscreen mode Exit fullscreen mode

Short explanation of the dependencies:

flask is the Python web framework we are gonna use.

psycopg2-binary is the driver to make the connection with the Postgres database.

Flask-SQLAlchemy is the ORM to make the queries to the database.

🐍 app.py file



The app.py file is the main file of the application: it contains all the endpoints and the logic of the application.

Populate the app.py file as follows:

from flask import Flask, request, jsonify, make_response
from flask_sqlalchemy import SQLAlchemy
from os import environ

app = Flask(__name__)
app.config['SQLALCHEMY_DATABASE_URI'] = environ.get('DB_URL')
db = SQLAlchemy(app)

class User(db.Model):
    __tablename__ = 'users'

    id = db.Column(db.Integer, primary_key=True)
    username = db.Column(db.String(80), unique=True, nullable=False)
    email = db.Column(db.String(120), unique=True, nullable=False)

    def json(self):
        return {'id': self.id,'username': self.username, 'email': self.email}

db.create_all()

#create a test route
@app.route('/test', methods=['GET'])
def test():
  return make_response(jsonify({'message': 'test route'}), 200)


# create a user
@app.route('/users', methods=['POST'])
def create_user():
  try:
    data = request.get_json()
    new_user = User(username=data['username'], email=data['email'])
    db.session.add(new_user)
    db.session.commit()
    return make_response(jsonify({'message': 'user created'}), 201)
  except e:
    return make_response(jsonify({'message': 'error creating user'}), 500