🎯 What you will learn
- A loop inside a loop is nested
- Each outer step runs the inner loop fully
- Shapes come from changing the row size
👋 Let’s get started!
Minecraft pyramids are built layer by layer, and each layer has more blocks. In code, a loop inside another loop does this. The outer loop picks the row, and the inner loop builds it. 🔺
🪜 Step by step
1. 🔺 Layers
The outer loop goes row by row.
for row in range(1, 4):
print("Row", row)2. 🧱 Blocks in a row
The inner loop places the blocks in each row.
for row in range(1, 4):
print("#" * row)3. ♟️ Checkerboard
Mix two blocks with if to make a pattern.
for r in range(2):
line = ""
for c in range(4):
line = line + ("X" if (r + c) % 2 == 0 else "O")
print(line)🧪 Try it!
Change the code and press ▶ Run to see what happens. You can’t break anything!
Pyramid and checkerboard
for row in range(1, 4):
print("#" * row)
print()
for r in range(2):
line = ""
for c in range(4):
line = line + ("X" if (r + c) % 2 == 0 else "O")
print(line)🎨 Unplugged activity
🔺 Draw a pyramid on graph paper: 1 square, then 2, then 3, up to 5. Then draw a checkerboard 4 squares wide. Compare your drawings with the code output.
Build a 4-step staircase
for step in range(1, 5):
print("#" * step)
print("Staircase done!")📖 Key words
Tap a card to flip it over!
- Nested loop
- A loop inside another loop 🪆
- Pattern
- Something that repeats in a shape 🌈
- % (modulo)
- Remainder after dividing; (r + c) % 2 alternates 0 and 1 ➗
🏆 Challenge
Print a pyramid with 3 rows: one #, then two #, then three #. Press ▶ Run.
Challenge
Knowledge Check Quiz
- What does "#" * 3 print?
- How many times does the inner loop run for each outer row?
- What is the second row of the checkerboard in the play example?