Lesson 9 of 12

For Loops 🔄

🎯 Grades 6–8 ⏱ ~25 minutes 💚 Intermediate

What You'll Learn

Use for loops to iterate over a range
Loop through lists
Use range() to control iterations

The For Loop

A for loop repeats code for each item in a sequence. It is perfect for going through lists or running code a specific number of times:

Python

# Loop through a list
fruits = ['apple', 'banana', 'cherry']
for fruit in fruits:
    print(f'I love {fruit}!')

# Loop 5 times using range()
for i in range(5):
    print(f'Count: {i}')

range() — Count with Control

Python

# range(stop)
for i in range(5):       # 0, 1, 2, 3, 4
    print(i)

# range(start, stop)
for i in range(1, 6):    # 1, 2, 3, 4, 5
    print(i)

# range(start, stop, step)
for i in range(0, 10, 2): # 0, 2, 4, 6, 8
    print(i)

💡

Off by One

range(5) gives 0,1,2,3,4 (five numbers). range(1,6) gives 1,2,3,4,5. The stop value is never included!

Accumulating with Loops

Python

# Add up all numbers 1 to 100
total = 0
for num in range(1, 101):
    total += num    # same as total = total + num
print(total)  # 5050

🔢">Times Table

Ask the user for a number. Print its multiplication table from 1 to 10 using a for loop. Example: 3 x 4 = 12

Quick Check

What does range(3) produce?

A1, 2, 3

B0, 1, 2, 3

C0, 1, 2

What does += mean?

AAdd and reassign (a += 1 means a = a + 1)

BGreater than or equal

CCheck equality

How do you loop through a list called 'items'?

Awhile items:

Bfor item in items:

Cloop item from items: