simple-app.md

Simple Flask App with SQLAlchemy

app.py

from flask import Flask
from flask_sqlalchemy import SQLAlchemy

# Initialize Flask App
app = Flask(__name__)

# Configure the SQLite database
app.config['SQLALCHEMY_DATABASE_URI'] = 'sqlite:///example.db'
app.config['SQLALCHEMY_TRACK_MODIFICATIONS'] = False

# Initialize the database
db = SQLAlchemy(app)

# Define a simple User model
class User(db.Model):
    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 __repr__(self):
        return f'<User {self.username}>'

# Create the database and tables
with app.app_context():
    db.create_all()

@app.route('/')
def home():
    return "Hello, Flask with SQLAlchemy!"

if __name__ == '__main__':
    app.run(debug=True)

Instructions to Run the Example

1. Install Dependencies:

   pip install Flask Flask-SQLAlchemy

2. Run the Application:

   python app.py

3. Open in Browser: Visit http://127.0.0.1:5000 to see the app running.

Explanation

• This example demonstrates setting up a simple Flask app with SQLAlchemy.
• We define a User model with id, username, and email columns.
• The database and tables are created using db.create_all().
• The home route returns a simple welcome message.

Next Steps

• Extend the app with CRUD operations.
• Connect to more advanced databases like PostgreSQL.
• Handle migrations with Flask-Migrate.