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

84 Chapter 5

are built-in constant values in Python. Python will not understand

if you type True as true without the capital T, and the same goes for

False.

You’re Not Old Enough!

Let’s write a program that uses Boolean conditional expressions to

see if you’re old enough to drive a car. Type the following in a new

window and save it as OldEnough.py.

OldEnough.py

u driving_age = eval(input("What is the legal driving age where you live? "))
v your_age = eval(input("How old are you? "))
w if your_age >= driving_age:
x print("You're old enough to drive!")
y if your_age < driving_age:
z print("Sorry, you can drive in", driving_age - your_age, "ye ars.")

At u, we ask the user for the legal driving age in their area,

evaluate the number they enter, and store that value in the vari-

able driving_age. At v, we ask for the user’s current age and store

that number in your_age.

The if statement at w checks to see if the user’s current age

is greater than or equal to the driving age. If w evaluates to True,

the program runs the code at x and prints, "You're old enough

to drive!". If the condition at w evaluates to False, the program

skips x and goes to y. At y, we check if the user’s age is less than

the driving age. If so, the program runs the code at z and tells the

user how many years it’ll be until they can drive by subtracting

driving_age from your_age and printing the result. Figure 5-4 shows

the results of this program for my son and me.