Django(Python) for backend. React for the front-end.

Pros:

+ You are already a bit familiar with Python

+ Django provides out of the box solutions for authentication, db management, migrations + bunch of stuff that takes quite a bit of effort

+ React is easy to grasp, since there isn't many buzzwords and concepts. Basically it's just JS.

Cons:

- You have to put effort in learning Javascript and browser fundamentals. There's no running away from it.

I built http://writango.com with the stack I mentioned. Literally took me a weekend to get the project's first version up.