Loops and Iteration

Loops let you run a block of code over and over again. This is called iteration. Instead of copying and pasting code 10 times, loops do the repeating for you.

Why Use Loops?

  • Efficiency: Save time by repeating code automatically.
  • Automation: Useful for lists, counting, checking input, and more.
  • Cleaner Code: Fewer lines, better structure.

Let’s start by watching a short video to understand how loops work in programming.

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The for Loop

for loops are great when you know how many times something should run. It repeats a fixed number of times.

for i in range(5):
    print(i)

This prints: 0 1 2 3 4

The while Loop

while loops run as long as a condition is true. It’s useful when you don’t know how many times the loop needs to run.

x = 0
while x < 5:
    print(x)
    x += 1

This also prints: 0 1 2 3 4

Comparing for and while

  • For loop: Use when you know how many times to repeat.
  • While loop: Use when you repeat until something changes.

Looping Through Lists

We can use loops to go through all items in a list.

fruits = ["apple", "banana", "cherry"]
for fruit in fruits:
    print(fruit)

Try It Yourself!

Try these short challenges on your own or with your group.

🍿 Popcorn Hack

What is the difference between a while loop and a for loop?


  






  





  
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    Homework Hacks
    
  
      
    
    1. Count Down: Use a while loop to print numbers from 10 to 1, then "Liftoff!".
      2. 
    
    2. Sum of Numbers: Write a for loop to find the sum of numbers 1 through 100.
      3. 
    
    3. Filter Even Numbers: Loop through a list and print only the even ones.
      4. 
  
    

  



    

  
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