Being a Python guy myself, the problem was never the lack of Python in the browser, it's always the lack of a Python ecosystem in the browser. If I'm going to use Python and awkwardly interface with JS, I might as well just use JS.

It makes me want to gouge my eyes out, but it's not really that hard to get productive in. CoffeeScript is even better, if you aren't averse to adding another dependency on top of everything else.