Earlier quoted context omitted.
There are actually quite a few Python-in-the-browser implementations, not just those two! A couple of years ago a colleague of mine wrote up a comparison, including Brython and Pyodide: https://anvil.works/blog/python-in-the-browser-talk (We chose one of the Python-to-JS compilers, https://skulpt.org , for the Anvil web-app platform, because it's much lighter weight than this. It's a couple of hundred kb on the wire,…
And before all of those, 20 years ago, ActiveState had a Python ActiveX extension (in addition to Perl and TCL).
Just the word "ActiveX" brings about nightmares.