It's possible to take a step further with a browser extension, but this is a basic Python project that hosts a web page that you can drag and drop a file on for a visualizer.

A new project from Anaconda delivers the Python runtime in a web page, via a single JS include, and with access to many popular Python packages.

Python might be the most popular programming language in the world, but unlike other frontrunner JavaScript, you can't run Python code in the browser.