Pyodide is a science-oriented suite, it's more than python. I haven't tried it, and it seems way too big, and seems too complex to build and/or use.
Brython provides some interfacing with the DOM, which is mandatory if it's replacing javascript.
Brython provides some interfacing with the DOM, which is mandatory if it's replacing javascript.
It seems easy to consume from the JS app POV, if you are using the builds from upstream.