Card 10: Iterating

Module 4: Data Structures

1 The Hook

Imagine a teacher taking the register.

She doesn't say "Everyone say 'Here' at once!"
She goes through the list, one by one.

This is Iteration. We loop through a list and handle each item individually.

2 Worked Example

Printing a menu.

menu = ["Burger", "Chips", "Soda"]

for item in menu: # 'item' becomes "Burger", then "Chips"...

print(item)

PREDICT

What happens to the numbers?

nums = [1, 2, 3]
for x in nums:
print(x * 10)

Interactive Editor

main.py

nums = [1, 2, 3]
for x in nums:
    print(x * 10)

Terminal Output

> _

BRONZE (MODIFY)

🥉 Colour Palette

1. Create a list of 3 colours: ['Red', 'Blue', 'Green'].
2. Loop through them.
3. Print "I like " + colour.

bronze.py

colours = ["...", "...", "..."]
for c in colours:
    print("I like", c)

> _

SILVER (FIX)

🥈 Missing Colon

This code fails because of a syntax error.
1. Fix the error (Add the :).
2. Make sure it prints "Code is Fun" 3 times.

silver.py

words = ["Code", "Is", "Fun"]
for w in words
    print(w)

> _

GOLD (MAKE)

🥇 Average Machine

1. Create a list: [10, 20, 30, 40].
2. Create a total (0).
3. Loop and sum them up.
4. Calculate average: total / 4.
5. Print the average (25.0).

gold.py

nums = [10, 20, 30, 40]
total = 0
for ...
    ...
print(...)

> _

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