Have you used extensions for Flask in your projects?

Yes, when developing with Flask, extensions are often used to add functionality and simplify development. For example:

• Flask-SQLAlchemy — for working with databases via ORM.
• Flask-Migrate — for managing database migrations.
• Flask-Login — for implementing user authentication.
• Flask-WTF — for working with web forms.

An example of using Flask-SQLAlchemy:

from flask import Flask
from flask_sqlalchemy import SQLAlchemy

app = Flask(__name__)
app.config['SQLALCHEMY_DATABASE_URI'] = 'sqlite:///test.db'
db = SQLAlchemy(app)

class User(db.Model):
    id = db.Column(db.Integer, primary_key=True)
    username = db.Column(db.String(80), unique=True, nullable=False)

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

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

Extensions help quickly add necessary features without writing a lot of code from scratch.