Is there a way that we can build a program or an application using just python , or we should mix some other languages?

Answer 1

Python is extremely powerful. There are many applications in just python, such as huge 3D modeling program called Blender. The good thing about python is that it has so many libraries and they are easy to install. So you can definitely make an application in python, but you will probably use a few libraries.

Answer 2

You can, but expect it to be extremely slow.

Never have I ever seen any real application written in Python, only Linux scripts.