Which one is better : Java or Python

Answer 1

Such questions are meaningless, because there are many languages. One might better fit your habits, your skill level and your project, your actual goals. Less others.
First question to yo is: better for what?

Answer 2

better for app development

Answer 3

Python is better in the sense it takes less lines to do the same thing in Java, but like zorgo mentioned, you should be asking what java is used for and what python is used for.

Answer 4

"better for app development" is still not concrete enough. For an enterprise class commercial application I would address java. But for example for some office automation I would simply use python. If you want to build web application, java needs heavy architecture, while you can even have a simple web server in python with several code lines. Python can be used as legacy cgi, while java not. Pyhon scripts can be modified just on the fly if needed, java compilation is not so simple... and so on.