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.

PyApp seems to be taking the Python world by storm, providing long-awaited click-and-run Python distribution. For developers ...

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 ...

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.

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.