Which of languages can we combine in programming projects? For example can we combine java and python or c++...etc ?

Answer 1

Yes.

For example, I sometimes write an application in python for rapid development and write core module (performs heavy computation) in C++ for better performance.

Usability depends on combination of languages and your purpose.

Answer 2

thanks, is there an example of any application that is programming with python + C++ ?

Answer 3

How about this doc?

https://docs.python.org/3.6/extending/extending.html#extending-python-with-c-or-c