Python's module system

Python's module system is something we have been using throughout the book. It is what lies behind the import statements.

All that we need to do in order to create a module is make a Python file. It really is that simple. Let's take a small example. Create a new folder to hold our example and add a short simple file:

# mymod.py
myvariable = 15

def do_a_thing():
    print('mymod is doing something')

def do_another_thing():
    print('mymod is doing something else, and myvariable is', myvariable)

This may look the same as any normal Python file, but we can treat this as a reusable module if we want to. To demonstrate, open up a terminal window, change into the directory you have just created with this file in, and then run the Python REPL:

>>> import mymod
>>> mymod.do_a
mymod.do_a_thing( mymod.do_another_thing( 
>>> mymod.do_a_thing()
mymod is doing something
>>> mymod.do_another_thing()
mymod is doing something else, and myvariable...