Flask Tutorial

Build real websites and APIs with Flask, the lightweight Python web framework — 52 lessons from your first route to a deployed full-stack app.

Learn Flask from scratch — routes, templates, forms, databases, blueprints, REST APIs and authentication — free interactive Python web-dev lessons.

👋 Know a little Python? You're ready for Flask.

Start with Lesson 1 and build a working web app step by step — at your own pace.

Continue where you left off

Lessons in this course

• Introduction to Flask — What Flask is, how to install it, and run your first web app with flask run
• Your First Route — Map URLs to Python functions with the @app.route decorator
• Dynamic Routes & Variables — Capture parts of the URL as variables and use type converters
• HTTP Methods (GET & POST) — Handle GET and POST requests and read submitted data
• Templates with Jinja2 — Render HTML pages with the Jinja2 templating engine
• Static Files (CSS, JS, Images) — Serve stylesheets, scripts, and images from the static folder
• Request & Response Objects — Inspect incoming requests and craft custom responses with headers and status codes
• Handling Forms — Collect, validate, and process user input from HTML forms
• Sessions & Cookies — Remember users across requests with signed sessions and cookies
• Flask Blueprints — Split a growing app into modular, reusable components
• Database with SQLAlchemy — Connect a database and define models with Flask-SQLAlchemy
• CRUD Operations — Create, read, update, and delete database records
• Database Migrations — Evolve your database schema safely with Flask-Migrate and Alembic
• Error Handling & Custom Pages — Catch errors and show friendly custom 404 and 500 pages
• Flashing Messages — Show one-time notifications like 'Saved!' after an action
• Building a REST API — Design RESTful endpoints that return JSON for any client
• JSON & Serialization — Convert Python objects to JSON and parse incoming JSON payloads
• Authentication & Login — Register, log in, and protect routes with Flask-Login and hashed passwords
• App Factory & Config — Structure production apps with the application factory pattern and config classes
• Testing Flask Apps — Write automated tests with the Flask test client and pytest
• Deploying Flask — Ship your app to production with Gunicorn and a real WSGI server
• Jinja2 Deep Dive: Filters, Macros & Inheritance — Master Jinja2 filters, loops, template inheritance, includes, and macros
• URL Building & Redirects with url_for — Generate URLs the safe way with url_for and redirect between views
• Working with Cookies — Set, read, and delete cookies with the right security flags
• Handling File Uploads — Accept file uploads safely with request.files and secure_filename
• Configuration & Environments — Manage settings with config objects, classes, and environment variables
• Application & Request Context (g, current_app) — Understand the app and request contexts, flask.g, and current_app
• Request Hooks (before/after_request) — Run code around every request with before_request and after_request
• Class-Based Views (MethodView) — Organize related handlers into classes with Flask's MethodView
• Checkpoint: A Dynamic Web App — Combine templates, cookies, hooks and class-based views — then a quiz
• User Login with Flask-Login — Add a login system with sessions, @login_required, and current_user
• Form Validation with Flask-WTF — Validate forms and block bad input with WTForms validators and CSRF
• SQLAlchemy Relationships — Model one-to-many and many-to-many relationships between tables
• Querying with SQLAlchemy — Filter, order, join, and aggregate with the modern select() API
• Pagination — Split long result sets into pages with offset/limit and page links
• CORS & Cross-Origin Requests — Allow browsers from other origins to call your API safely
• API Authentication with JWT — Issue and verify JSON Web Tokens to protect your API endpoints
• Serialization with Marshmallow — Serialize and validate API data with Marshmallow schemas
• Checkpoint: Build a REST API — Combine models, queries, schemas and pagination into a JSON API — then a quiz
• Caching with Flask-Caching — Speed up responses with view, memoize, and backend caching
• Rate Limiting (Flask-Limiter) — Protect APIs with per-route limits and 429 responses
• Background Tasks (Celery & RQ) — Offload slow work to a worker queue and return instantly
• Real-Time with WebSockets (Flask-SocketIO) — Push live updates with WebSocket events, rooms, and broadcasts
• Sending Email (Flask-Mail) — Send plain-text and HTML email with attachments from a request
• Logging & Monitoring — Configure app.logger, structured logs, and error reporting
• Custom CLI Commands (flask CLI) — Add your own flask commands with click options and arguments
• Signals (Blinker) — Decouple code by reacting to request and template signals
• Async Views & ASGI — Write async def views and run Flask under an ASGI server
• Checkpoint: Production-Ready Flask — Combine caching, rate limiting, tasks and logging — then a quiz
• Capstone: A Full CRUD App — Combine everything into a complete database-backed web application
• API Docs with OpenAPI & Swagger — Auto-generate interactive Swagger docs with flask-smorest and marshmallow schemas
• DB Transactions & Query Optimization — Commit/rollback safely, then speed queries with indexes and eager loading

More for this course

• Flask cheat sheet — Quick syntax reference you can scan while you code