Decisions with if

What you'll learn

Read input with input() and turn it into numbers with int()
Compare values (<, >, ==, …)
Take different paths with if, elif and else

The computer asks back

With input() your program can ask you something. Try it – an input field appears below the editor:

name = input("What's your name? ")
print(f"Hi {name}, great to have you here!")

Important: input() always returns text, even if you type a number. To calculate you have to turn it into a whole number with int():

number = int(input("Enter a number: "))
print(f"Double that is {number * 2}.")

Comparing

A comparison always gives True or False:

Sign	Meaning	Example
`<`	less than	`3 < 5` → `True`
`>`	greater than	`3 > 5` → `False`
`<=`	less than or equal	`5 <= 5` → `True`
`>=`	greater than or equal	`4 >= 5` → `False`
`==`	equal	`2 + 2 == 4` → `True`
`!=`	not equal	`"a" != "b"` → `True`

Watch out: One = stores a value, two == compare. Everybody mixes them up at the start.

if, elif, else

With if your program decides which code runs. Everything that is indented (4 spaces) belongs to the if.

temperature = 28

if temperature > 25:
    print("Off to the pool!")
elif temperature > 15:
    print("Perfect for cycling.")
else:
    print("Better stay in and code.")

print("This line always runs.")

Python checks from top to bottom and takes the first path that fits – after that the others are skipped. Change the temperature to 20 and to 5 and use Steps to see which lines are skipped.

Remember: After if, elif and else there’s always a colon :. The next line is indented.

Quick check

Before you start the task: what does this program print? Type your guess – then Python works it out.

points = 7
if points > 8:
    print("great")
elif points > 5:
    print("good")
else:
    print("keep practising")

Your task

Your turn

A cinema sells tickets by age. Ask for the age with input() and print the right ticket: under 14 years Child ticket: 5 euros, 65 and over Senior ticket: 6 euros, everyone else Standard ticket: 9 euros.

age = int(input("How old are you? "))

# Decide here which ticket fits:

Something to think about
At age 10 exactly “Child ticket: 5 euros” should appear – and no other ticket.
Which command helps?
14 is no longer “under 14”. Check whether you use < or <=.
“65 and over” means 65 is included – so >= 65.

Gap code – fill in the ___

                        age = int(input("How old are you? "))

if ___:
    print(___)
elif ___:
    print(___)
else:
    print(___)

Solve it without hints to earn a ⭐ on your progress page.

Show solution

Try it yourself first – mistakes teach you the most. Here is one possible solution:

age = int(input("How old are you? "))

if age < 14:
    print("Child ticket: 5 euros")
elif age >= 65:
    print("Senior ticket: 6 euros")
else:
    print("Standard ticket: 9 euros")

For fast learners

Pro task

Is year a leap year? The rule: a year is a leap year if it can be divided by 4 – unless it can be divided by 100. But if it can be divided by 400, it's a leap year after all. Print 2024 is a leap year. or 2023 is not a leap year. (with the real year).

year = 2024

# Leap year or not?

Show pro solution

year = 2024

if year % 4 == 0 and (year % 100 != 0 or year % 400 == 0):
    print(f"{year} is a leap year.")
else:
    print(f"{year} is not a leap year.")

Practise more in the training roomEndless new tasks on this topic – with XP and streaks.