Can JSP and Python used together for same database?
We are planning an android app in this summer and I'm considering
  developing it with Python

Native Android apps are developed using Java.

However, the service provided by the app is supposed to be added to
  the website made with JSP later. I'm afraid the difference of the
  language would cause any obstacle.

You will need to create an API that communicates between Android and your database.
I'm a student who work part-time at a start-up, which runs a website made with JSP.
We are planning an android app in this summer and I'm considering developing it with Python, which I'm interested in.
However, the service provided by the app is supposed to be added to the website made with JSP later.  I'm afraid the difference of the language would cause any obstacle.
Since they will use a common database, I think using different languages to access it won't have any problem.  I want to make sure that my guess is correct.
Pardon my poor English.  I'd appreciate your answers.