Q: I have couple of questions about what is preffered, using Java in server-side or Python? [on hold]

I am currently considering going deep with Java an its technologies in server-side web development (Learning about Spring, Servlets, Apache/Tomcat and the like) or with Python/Django. Regardless, I think I will use them both in the server-side, but I am considering what is gonna be the main language in the back-end (the one that I will have to learn all the technologies regard to web development), and the side one.

I have a question regard that:

What language is preferred in server-side as the primary language (Taking into account rapid development, security, fast, scalable).

Thanks ahead you guys!