PyScript lets you run Python scripts right in the browser, side by side with JavaScript, with two-way interaction between your code and the web page.

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.

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.