Lona is a web application framework, designed to write responsive web apps in full Python. Web is a solved problem in Python since ages, but traditionally Python handles only the server side. If you want to have client side interaction like click events or you want update content live, you have to write an additional Javascript application. Lona handles the server side and the client side, and provides a simple, pythonic API to write self contained views. Lona comes with a Javascript based browser library that speaks a specialized protocol with the backend. This protocol specifies messages like "hey frontend, please show $HTML" and "hey backend, someone clicked on node XY"