Lesson 18 of 20 · If & Then

If & Then — Part 18

If something is true, do this. Otherwise do something else.

What you'll learn

You will learn how if/else lets code make decisions based on whether something is true or false.

Words to know

Condition: A check that can be true or false. The program chooses what to do based on it.
if: A keyword that means 'when this is true, do this block of code.'
else: A keyword that means 'otherwise, when the if is not true, do this block instead.'

Your turn

📋 Show the steps

Press ▶ Run and see what the computer says!

1Read the code. x is set to True. The 'if x:' line checks: is x true? Since it is, the code prints 'Yes!'
2The 'else' block only runs when the condition is NOT true. Since x IS True, the 'No!' line gets skipped entirely.
3If x were False instead, the computer would skip 'Yes!' and print 'No!' instead. One condition, two possible paths!
4Conditions let programs make decisions — like a fork in the road. 'if' goes one way, 'else' goes the other.

Auto-run is on: change the code and the result updates by itself.

Auto-run

Output

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Check your understanding · 1 of 5

A condition can be:

Check your understanding · 2 of 5

What does 'if' do in Python?

Check your understanding · 3 of 5

x = 5 if x > 3: print('Big') What prints?

Check your understanding · 4 of 5

What does 'else' mean?

Check your understanding · 5 of 5

x = 2 if x > 10: print('Yes') else: print('No') What prints?

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