PyScript, which is, of course, Python in the browser. The tool is in the early experimental phase, so the project doesn’t suggest using it in a production environment yet.

In the December update to Python in Visual Studio Code, developers can experiment with a new preview feature that lets them run and debug Python code in the browser.

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.