Python Projects for Beginners a ten-Week Bootcamp Approach to Python Programming

CHAPTER 5
Functions
This week begins the topic of functions. Along with loops, functions can be one of the tougher topics to understand. For this reason, this entire week has been dedicated to covering functions only. This is also one of the more important topics in programming.
Knowing how to use a function will greatly improve your programming skills.
Functions give us the ability to make our programs much more powerful and clean while also saving us time. We’ll go over how they work on the first day, but the reason we use functions is because of the ability to write once and call repeatedly.
Many of the programs that we’ve already built can benefit from the use of functions, especially games like Hangman. At the end of the week, we’ll build a program that resembles a shopping cart list. We’ll see why it’s important to separate tasks such as adding, removing, and displaying into separate functions.
Overview

• 
  How to use functions and what they are
  
• 
  Passing data around using parameters
  
• 
  Returning data from functions
  
• 
  Understanding scope and its importance
  
• 
  Creating a shopping cart program
  

CHALLENGE QUESTION
Remember that an algorithm is nothing more than a set of step-by-step instructions. If we were to write an algorithm for changing a light bulb, what would it look like? What problems do you have to consider? How many steps are necessary? What is the most efficient method? Using the following algorithm, what problems may occur?
© Connor P. Milliken 2020
C. P. Milliken, Python Projects for Beginners, https://doi.org/10.1007/978-1-4842-5355-7_5

1. 
   Retrieve spare bulb.
   
2. 
   Turn off switch powering current bulb.
   
3. 
   Unscrew current bulb.
   
4. 
   Screw in spare bulb.
   
5. 
   Turn on switch powering new bulb.
   
6. 
   If spare bulb does not turn on, repeat steps 1 through 5.