My comment here would be that while you could probably learn enough python to do everything you needed at this point, there’s still domain knowledge and learning required to build a web application. If you’ve already done this in JavaScript or Rails, not a problem - though if you had, I don’t know why you’d need to learn python to build the prototype?
I’ve been using python as a data scientist for about 3 years now. While I can do everything I ever need to for general processing and analytical tasks, I STILL feel like I have a huge tech debt on the front end that I wish had begun paying off much earlier.