The Python web framework created by Armin Ronacher is Flask.
Flask is a lightweight web framework for Python, commonly described as a microframework because its core does not force a database layer, form system, or other large collection of built-in components. Instead, developers can add functionality through extensions. Flask is built around Werkzeug, a WSGI utility library, and commonly uses Jinja for templates; these projects emerged from the Pocoo group of Python enthusiasts.
Flask’s origin has an unusual twist. Ronacher initially presented the idea as an April Fool’s joke: a compact framework bundled together several of his existing libraries. The concept proved popular enough to become a serious project, with Flask’s first release arriving in 2010. Development later moved from Pocoo to the Pallets organization.
Tornado, Pyramid, and Django are also Python web frameworks, which makes them plausible distractors. Django is a larger, more batteries-included framework, while Flask emphasizes a smaller core and developer choice.