Importing Numpy into functions
You have to import modules in every file in which you use them.  Does that answer your question?
I do not know the right way to import modules.
I have a main file which initializes the code, does some preliminary calculations etc.
I also have 5 functions f1, f2, ... f5. The main code and all functions need Numpy. 
If I define all functions in the main file, the code runs fine.
(Importing with : import numpy as np)
If I put the functions in a separate file, I get an error:
Error : Global name 'linalg' is not defined. 
What is the right way to import modules such that the functions f1 - f5 can access the Numpy functionality?