Storing Functions in Modules

A
module is simply a file that contains Python code. A large program can be made
into smaller modules, and each module contains functions that perform related
tasks. With this Large programs are
easier to debug and maintain when they are divided into modules.

This approach, which is called modularization,
makes the program easier to understand, test, and maintain.

Modules also make it easier to reuse the same code
in more than one program. Import the module in each program that needs to call one
of the module functions.

import circle

When the Python interpreter reads this statement it
will look for the file circle.py in the same folder as the program that is
trying to import it. If it finds the file, it will load it into memory. If it
does not find the file, an error occurs. Once a module is imported you can call
its functions.