Learn FLASK with Real Code Examples

Flask provides a micro-framework approach, giving only essential features by default.

It uses Werkzeug for WSGI and Jinja2 for templating.

Supports extensions for database integration, authentication, form validation, and more.

Built-in development server and debugger for easy testing.

Widely used for web APIs, microservices, and small to medium web applications.

Routing with decorators (`@app.route`) for HTTP methods

Request and response objects for handling HTTP traffic

Template rendering with Jinja2

Support for sessions and cookies

Extension mechanism for adding functionality

Flask app instance - core object

Routes - define endpoints using decorators

Templates - render HTML via Jinja2

Extensions - add ORM, authentication, caching, etc.

Request/Response - manage incoming/outgoing HTTP traffic

app.py - main application file

templates/ - HTML templates

static/ - static assets (CSS, JS, images)

extensions/ - optional modular extensions

routes/ or blueprints/ - for modular route organization

Create Flask app with `Flask(__name__)`

Define routes using `@app.route`

Use templates for dynamic HTML

Integrate extensions for databases or authentication

Run the server with `app.run()`

Beginner: simple GET/POST endpoints

Intermediate: CRUD API with SQLite/PostgreSQL

Advanced: authentication, authorization, REST API

Expert: microservices with Blueprints and Celery

Auditor: optimize for performance and security

Flask vs Django: Flask is lightweight and flexible, Django is full-featured and opinionated

Flask vs FastAPI: FastAPI supports async and type hints, Flask is synchronous

Flask vs Fastify: Flask is Python, Fastify is Node.js with high performance

Flask vs Tornado: Tornado is async-first, Flask is simple WSGI-based

Flask vs Pyramid: Pyramid is more configurable, Flask is minimal and simple

2010 – Flask initial release

2011–2013 – Widespread adoption and extensions

2015 – Flask 0.11 with blueprints and improved testing

2017–2020 – Python 3 support and async improvements

2022–2025 – Async support, security, and performance improvements

Flask app instance - core object of application

Route - HTTP endpoint defined with decorator

Template - HTML with dynamic content via Jinja2

Extension - adds features like ORM, auth, caching

Request/Response - HTTP objects for input/output