Flask Micro Web Framework

Flask is a free and open-source micro web framework written in Python, classified as a microframework because it keeps the core simple but extensible. Created by Armin Ronacher in 2010, Flask is one of the most popular Python web frameworks, used by Netflix, Reddit, LinkedIn, and Pinterest. Key features: minimal core: provides only essentials (routing, request/response, templating) with no built-in database abstraction, form validation, or authentication. The core is under 2,500 lines, giving developers freedom to choose their own tools. Routing via Python decorators (@app.route('/')). Jinja2 templating with template inheritance, autoescaping, and sandboxed execution. Werkzeug WSGI: built on Werkzeug providing request/response objects, routing, debugging, and development server. Development server with hot reloading and interactive debugger. Blueprints: organize components into modules for large application structure. Extensions: Flask-SQLAlchemy (database), Flask-Login (auth), Flask-WTF (forms/CSRF), Flask-Mail, Flask-Caching, Flask-RESTful, Flask-SocketIO. Signals: event notification system for loose coupling. Application and request context separation. Click CLI for custom management commands. Python codebase. BSD-3-Clause.