The bus reader makes a choice

You tap your card on the bus. The reader asks itself some questions. Is this a child? Is this a student? Is it after 9am?

Each answer changes the price. A program does the same. It follows steps in order. At some steps it makes a choice. In this lesson you learn both.

Key words

Word	What it means	Example
Sequence	Steps that run one after another, from the top to the bottom.	print, then print
Selection	A choice. The program picks one path.	if age < 16
Condition	A question with the answer True or False.	age < 16
if	Runs its lines only when the condition is True.
elif	Short for else if. It tests another condition when the ones above were False.
else	Runs when no condition above was True.
match case	Compares one value with a list of patterns and picks the first that fits.
Indentation	The spaces at the start of a line. They show which lines belong inside the if.
Flowchart	A picture of steps and decisions, drawn with symbols and arrows.

The cells students fill in are left blank in this preview.

Sequence: one step after another

A sequence is a list of steps that run in order. Python starts at the top and goes down. It does not skip a line unless you ask it to.

Order matters. You cannot take your ticket before you tap your card.

Try it: steps in order

Code: python

print("1. Tap your card")
print("2. The reader checks the fare")
print("3. Take your ticket")

# Swap line 1 and line 3, then run it again.
# The steps still run in order. But now the order is wrong.