I'm a back end C++/rust type and I script with Python.
If I wanted to build a front end, is there any reason I'd use Ruby/Rails over Django? I'm not familiar with Rails but I'm curious if it's worthwhile to pick up.
Whether it's worth it for you to learn or not depends on how quickly you can pick it up and how important the web app part is to you.
Edit: Why is yazmeya's sibling comment flagged? It's not a glib one-liner and it's clearly an attempt to be helpful.
That said, I would argue that Ruby is a very similar but nicer scripting language than Python (particularly for general utility / glue scripts), so if you enjoy scripting in Python you would probably find Ruby easy to pick up and potentially a nice compliment to what you already know.