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.

Playwright, a Python library, allows developers to essentially control the browser with a few lines of Python code to automate cross-browser testing for single-page web apps and Progressive Web Apps.

With trinket.io, you can run python scripts in your browser. Even cooler is that they also run on your phone.

Microsoft plans to enable the Python and Ruby languages to be used for client-side development of rich Internet applications that leverage the company’s Silverlight browser plug-in technology ...

Microsoft plans to enable the Python and Ruby languages to be used for client-side development of rich Internet applications that leverage the companyu2019s Silverlight browser plug-in technology.

Syntax highlighting in Python code -- along with other language-specific "smartness" -- is provided in Microsoft's Python extension for VS Code via the Pylance language server, and that's where the ...

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.