Using Custom Modules

Sometimes, we might want to use a module that python doesn’t come with by default. We’ll call these modules “custom modules”.

When we talk about using custom modules, it’s important to understand that a module is really just a nicely encapsulated collection of functions.

Let’s say, for example, that the instructor of your class wanted to provide you with some pre-written functions to use in your homework. Rather than telling you to copy + paste the functions into your program, they would like to provide them as a module so that you can use the functions in your program, but not modify their contents.

To do this, your instructor will provide you with code as a .py file, for example secrets.py.

The contents of secrets.py may look something like the following:

def hello(name):
    print("Hello " + name)
    print("This greeting came from the hw1 module!")
    
def goodbye():
    print("Goodbye from the hw1 module)
    

Now, the question becomes, how does one go about actually using the code your instructor provided as a module?

Step 1: Ensure that the module is in the proper location

To access a module that has been provided as a .py file, the .py file needs to be in the same folder as your program.

For example, you may be working in your homework2/ folder, which is located in your computer_science folder:

computer_science/
    homework1/
        homework1.ipynb
    homework2/
        homework2.ipynb

To use the module that your instructor has provided in homework2.ipynb, it should be placed in your homework2 folder:

computer_science/
    homework1/
        homework1.ipynb
    homework2/
        homework2.ipynb
        secrets.py

Step 2: Import the module

Now that the files are in the appropriate locations, we can use the functions in the module after we import the module in our code.

import secrets

secrets.hello("Spock")
secrets.goodbye()