Flask: A Python Framework You Should be Using Today

Flask gives you the bare minimum to build a web application, then gets out of your way. No ORM. No form validation. No admin panel. Just routing, templates, and request handling. Everything else is your choice.

That sounds terrible if you're used to Django or Rails handing you everything on a silver platter. But Flask's minimalism is the point. You only include what you need. Your API doesn't need templates? Don't use them. Your app doesn't need a database? Don't add one. Flask trusts you to make those decisions.

from flask import Flask

app = Flask(__name__)

@app.route('/')
def hello():
    return 'Hello World'

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

That's a complete Flask application. Five lines. No configuration files. No project structure. No magic. You can understand the entire thing in ten seconds.

Flask Grows With You

The "micro" in microframework doesn't mean Flask can't handle serious applications. Instagram ran on Flask for years. Netflix uses Flask for some services. The framework scales just fine. It just doesn't force patterns on you from day one.

When your app gets bigger, you add structure through Blueprints. Blueprints let you split your application into logical modules without changing how Flask works. Your user authentication can live in one Blueprint, your API in another, and your admin panel in a third.

from flask import Blueprint

auth = Blueprint('auth', __name__)

@auth.route('/login')
def login():
    return render_template('login.html')

@auth.route('/logout')
def logout():
    # logout logic
    pass

Register your Blueprints with the main app and Flask handles the routing. You can even mount Blueprints at different URL prefixes. It's simple, obvious, and doesn't involve learning a framework-specific architecture.

The Extension Ecosystem

Flask's philosophy is "bring your own batteries." The community built extensions for everything you might need. Flask-SQLAlchemy adds an ORM. Flask-Login handles authentication. Flask-WTF manages forms. Flask-RESTful makes building APIs easier. Flask-CORS deals with cross-origin requests.

from flask import Flask
from flask_sqlalchemy import SQLAlchemy
from flask_login import LoginManager

app = Flask(__name__)
app.config['SQLALCHEMY_DATABASE_URI'] = 'postgresql://user:pass@localhost/db'

db = SQLAlchemy(app)
login = LoginManager(app)

These extensions integrate with Flask without taking over. You still write Flask code. The extensions just add functionality through familiar patterns. Most extensions work together without conflicts because they follow the same conventions.

Perfect for APIs

Flask shines when you're building APIs. The framework doesn't assume you need HTML templates or form handling. Return JSON from a route and Flask handles the serialization. Need API versioning? Use Blueprints. Need authentication? Flask-JWT or Flask-HTTPAuth plugs right in.

from flask import Flask, jsonify, request

app = Flask(__name__)

@app.route('/api/users', methods=['GET'])
def get_users():
    users = User.query.all()
    return jsonify([user.to_dict() for user in users])

@app.route('/api/users', methods=['POST'])
def create_user():
    data = request.get_json()
    user = User(**data)
    db.session.add(user)
    db.session.commit()
    return jsonify(user.to_dict()), 201

No ceremony. No configuration. Just routes that return data. Flask handles the HTTP details while you focus on business logic.

When Flask Isn't Enough

Flask works great until it doesn't. If you're building a traditional web application with forms, admin panels, and lots of CRUD, Django saves you time. Django includes everything out of the box. You'll spend less time choosing extensions and more time shipping features.

Flask also lags behind FastAPI for high-performance APIs. FastAPI has async support built in, automatic OpenAPI documentation, and better type checking through Pydantic. If you're building a pure API and performance matters, FastAPI is worth considering.

The flip side: Flask is mature. It's been around since 2010. The ecosystem is stable. You can find answers to any question. FastAPI is newer and moving faster, which means breaking changes and less Stack Overflow help.

Where Flask Fits

Flask is the right tool for specific jobs. Building an API for a mobile app? Flask gets you there fast. Prototyping a web service? Flask lets you iterate quickly. Building internal tools? Flask doesn't force you to fight the framework.

The best Flask projects have clear boundaries. You know what you're building. You know what extensions you need. You're not trying to build the next Facebook. Flask gives you exactly what you ask for, nothing more.

The Learning Curve

Flask is easy to learn but hard to master. The basics take an afternoon. Routes, templates, and request handling are straightforward. The hard part is knowing which extensions to use and how to structure your application.

Django tells you how to organize your code. Flask doesn't. That freedom is liberating once you know what you're doing. It's paralyzing when you're starting out. You can build a Flask app a dozen different ways and they'll all work. Picking the right way for your project takes experience.

The Flask community is helpful but smaller than Django's. The official documentation is excellent but assumes you know what you're doing. Expect to spend time reading extension docs and figuring out integration patterns.

Flask won't hold your hand. It won't make architectural decisions for you. It won't prevent you from shooting yourself in the foot. But if you want control over your stack and you're willing to make your own choices, Flask is hard to beat. It's the framework that respects your intelligence and trusts you to know what you need.