A. What is a Loop (For Loop)?

⏱️ 5 min B. The range() Number Factory →

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🎯 Learning Goals

By the end of this lesson, you'll be able to:

• ○ for Understand what a loop is
• ○ Understand why we use loops
• ○ Understand the basic structure of a loop

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Core Concepts

What is a loop?

Loopsis a way to run the same code multiple times.

🎠 Analogy: a carousel

Just like a carouselLike this, it spins a set number of times, repeating the same thing!

Why do we use loops?

# ❌ Without a loop (inefficient)
print("Hi!")
print("Hi!")
print("Hi!")

# ✅ Using a loop (efficient)
for i in range(3):
    print("Hi!")

Advantage: - Code is short and clean - Easy to edit - Prevents mistakes

for syntax

for i in range(count):
    to repeat Code

Element	Role
for	loop-start keyword
i	the variable that holds the current number
in	the connecting word meaning "from"
range(count)	creates a bundle of numbers
:	the signal that the loop body begins

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🍕 Visualization: the feel of a for loop “repeating automatically”

If loops are hard to grasp just in your head, it helps to check out the demo below first.

• The hard way (No Loop): To deliver to 5 houses, you'd have to write the go_to_house(10), go_to_house(11) … command 5 times, like this.
• The smart way (For Loop): for i in houses:If you write it like this, Variable iautomatically changes to the house number while repeating the same command. (In the demo, ichanges like a sticky note!)

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Example Code

from ursina import *

app = Ursina()

# Repeat 3 times to make cubes
for i in range(3):
    Entity(model='cube', position=(i*2, 0, 0))

app.run()

What Happens

Three cubes appear in a row!

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Quiz

Quiz: Loop keyword

What keyword starts a loop?

Check answers

Show Answer

Answer: for

foris the keyword that starts a loop.

for i in range(3):
    print(i)

for loop syntax practice:

• Loop start: i in range(3):
• Create a bundle of numbers: for i in (5):
• Loop-start signal: for i in range(3)

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🔧 Debug Clinic

Problem: I'm getting a SyntaxError!

❌ Wrong Code

for i in range(3)  # No colon!
    print(i)

Error message: SyntaxError: expected ':'

Cause: for At the end of the statement, a colon (:) is missing

✅ Correct Code

for i in range(3):  # Has a colon!
    print(i)

Fix: for At the end of the statement, a colon (:)!

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Try Coding It Yourself

Take what you learned with the blocks and write it yourself in Python code!

Using a for loop

for i in range(3):Try repeating 3 times with this.

Example Answer

for i in range(3):
    print('Hello!')

Result: 'Hello!' is printed 3 times!

Try changing the number of repetitions

Change the number inside range() to repeat a different number of times!

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🎯 Fill-in-the-Blank Mission

Fill in the blanks to complete the code!

Check answers

for i in range(4):
    print('Repeat!')

Check answers

for i in range(6):
    print(i)

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🧩 Key Takeaways

What you learned in this lesson:

Concept	Description
for	the keyword that starts a loop
i	the variable that holds the current loop number
range(n)	creates a bundle of numbers to repeat n times
Colon (:)	the signal that the loop body begins

Review Checklist

• [ ] for Can you explain what a loop is?
• [ ] Do you know what advantages using a loop gives you?
• [ ] for i in range(3): Do you know why a colon is needed after it?

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⏱️ 5 min B. The range() Number Factory →