Running Pythonfrom Terminal?

[34Ck30xN008]

I am taking a python class and was running ubuntu 14.10 until I had to replace the hdd and figured I would run Backbox instead.
normally I would open a terminal nav to my directory and type "python3 file_name.py" and my script would run and display what returned.
this is not the case. why, and what do I do to be able to run and test my programs?
thank you

[ZEROF]

Hi,

Install python 3.

[Fantasy]

Either you need to install Python or add its directoy to the PATH variable, so it can be executed from anywhere.