Conditionals

python  · 
📊 Workshop Slides

Understanding Indentation

Remember how important indentation is in Python?

for i in range(5):
    basic.show_string("Hello!")  # This line is indented - it's INSIDE the loop

The space at the beginning of the second line is called indentation. It tells Python that this code belongs inside the loop.

What happens if we don’t indent?

for i in range(5):
basic.show_string("Hello!")  # This line is NOT indented - it's OUTSIDE the loop

This only prints “Hello!” once instead of 5 times! Why?

Answer: Because basic.show_string("Hello!") is outside of the loop.

Your Turn!

What does this print out?

for i in range(5):
    basic.show_string("Hello!")  
   
basic.show_string("Bye!")
Answer

5 lines of “Hello!” followed by 1 line of “Bye!”

The “Hello!” is inside the loop (indented), so it repeats 5 times. The “Bye!” is outside the loop (not indented), so it only prints once.

Conditional Operators!

We’ve seen arithmetic operators before:

Now let’s learn about comparison operators, which compare two values:

Pop Quiz!

Is this true or false?

1000 > 3
Answer

True!

1000 is greater than 3.

Is this true or false?

9 < 8
Answer

False!

9 is not less than 8.

Is this true or false?

5 == 5
Answer

True!

5 equals 5.

Is this true or false?

45 == 93
Answer

False!

45 does not equal 93.

If Statements

What if we wanted to show something based on a condition? For example:

We can use if statements! They look like this:

num = 1
if (num == 1):
    basic.show_icon(IconNames.HAPPY)

Elif (Else If)

elif means “else, if”. In this case, if num isn’t 1, we check if num is 2:

num = 1
if (num == 1):
    basic.show_icon(IconNames.HAPPY)
elif(num == 2):
    basic.show_icon(IconNames.SAD)

Else

If num is neither 1 or 2, then we use else:

num = 1
if (num == 1):
    basic.show_icon(IconNames.HAPPY)
elif(num == 2):
    basic.show_icon(IconNames.SAD)
else:
    basic.show_icon(IconNames.MEH)

Your Turn!

Try copying and then changing num to 1, 2, and 3 before running your code:

num = 1
if (num == 1):
    basic.show_icon(IconNames.HAPPY)
elif(num == 2):
    basic.show_icon(IconNames.SAD)
else:
    basic.show_icon(IconNames.MEH)

Random Numbers

We can also make random numbers!

number = randint(1, 10)

This will generate a random number from 1 to 10.

Pop Quiz!

What numbers will this generate?

number = randint(1, 3)
Answer

Numbers from 1 to 3!

randint(1, 3) generates: 1, 2, or 3.

Your Turn: Make a Magic 8 Ball! 🔮

Let’s create a Magic 8 Ball that gives random answers when you shake it!

The Plan

Forever:

Step 1: Start a Forever Loop

while True:
    if input.is_gesture(Gesture.SHAKE):
        # Generate a new random image from these options: Yes, No, Meh

Step 2: Add Random Number Generation

while True:
    if input.is_gesture(Gesture.SHAKE):
        number = randint(1, 3)  # will give us a random number: 1, 2, or 3
        if number == 3:
            # YES
        elif number == 2:
            # NO
        else:
            # MEH

Step 3: Add the Icons

while True:
    if input.is_gesture(Gesture.SHAKE):
        number = randint(1, 3)
        if number == 3:
            basic.show_icon(IconNames.YES)
        elif number == 2:
            basic.show_icon(IconNames.NO)
        else:
            basic.show_icon(IconNames.MEH)

Complete Magic 8 Ball Code

while True:
    if input.is_gesture(Gesture.SHAKE):
        number = randint(1, 3)
        if number == 3:
            basic.show_icon(IconNames.YES)
        elif number == 2:
            basic.show_icon(IconNames.NO)
        else:
            basic.show_icon(IconNames.MEH)

Try it out! Shake your micro:bit and see what answer you get! 🔮

Customize Your Magic 8 Ball

Try these modifications:

Extra Challenges

Try these challenges:

References and Acknowledgements