Learn Python the Hard Way: A Deceptively Simple Introduction to the Terrifyingly Beautiful World of Computers and Data Science, 5th Edition

Exercise 18

Names, Variables, Code, Functions

Big title, right? I am about to introduce you to the function! Dum dum dah! Every programmer will go on and on about functions and all the different ideas about how they work and what they do, but I will give you the simplest explanation you can use right now.

Functions do three things:

1. They name pieces of code the way variables name strings and numbers

2. They take arguments the way Python scripts take argv in Exercise 13

3. Using 1 and 2, they let you make your own “mini-scripts” or “tiny commands”

You can create an empty function by using the word def in Python like this:

Listing 18.1: ex18_demo.py

1   def do_nothing():
2       pass

This creates the function, but the pass keyword tells Python this function ...