Teach Your Kids To Code: A Parent-friendly Guide to Python Programming

78 Chapter 5

In each of these cases, the computer checks a set of conditions:

Is the temperature too cold? Is there something in the path of the

car? Does the email look like spam?

In Chapter 4, we saw a statement that uses a condition to

make a decision: the while statement. In those examples, the condi-

tion told the while loop how many times to run. What if we wanted

to make decisions about whether to run a set of statements at all?

Imagine if we could write one program and let the user decide

whether they wanted circles or other shapes on their spiral. Or

what if we wanted circles and other shapes, like in Figure 5-1?

Figure 5-1: A spiral of rosettes and smaller spirals,

courtesy of an if statement

The statement that makes all this

possible is the if statement. It asks if

something is true, and based on the

answer, it decides whether to perform a

set of actions or skip over them. If the

temperature in a building is fine, the

heating and cooling system doesn’t run,

but if it’s too hot or too cold, the system

turns on. If it’s raining outside, you