6.1. Decision Making

One of the key features of any programming language is the ability to decide whether to run a segment of code. This means you can execute a set of statements only if a given condition is met.

Example

Consider an application that reminds you when you have an overdue book. The app sends you a message only if the due date has passed and you have not returned the book.

The condition in the example above depends on the status of the book. If the condition is true (the book is overdue), a message gets sent. If the condition is false, then the app does not pester you.

In general, we set up decision making in Python by using the following structure:

if condition_is_true:
   # Run this code
else:
   # Run this other code

We will dive into the details soon, but first we need to understand how Python determines if a condition is true or false.