range(), Counting Made Easy

The function behind every for loop, master it separately first

In the next lesson you'll learn for loops, the tool for repeating actions. But almost every for loop uses a function called range(), and beginners trip over it constantly.
So we're learning range() on its own first. Trust the process.

range(stop), count from 0
range(n) generates numbers starting from 0, up to (but NOT including) n.
range(5) → 0, 1, 2, 3, 4 (not 5, it stops before 5)
This trips up everyone at first. Remember: range stops before the number you give it.

Visualizing range()python

# Easiest way to see what range produces:
print(list(range(5)))    # [0, 1, 2, 3, 4]
print(list(range(3)))    # [0, 1, 2]
print(list(range(1)))    # [0]
print(list(range(0)))    # []  (empty, nothing before 0)

range(start, stop), control where you begin
range(1, 6) → 1, 2, 3, 4, 5 (starts at 1, stops before 6)range(5, 10) → 5, 6, 7, 8, 9range(0, 5) → same as range(5)

range(start, stop, step), skip numbers
The third argument controls the step size, how much to add each time.
range(0, 10, 2) → 0, 2, 4, 6, 8 (even numbers)range(1, 10, 2) → 1, 3, 5, 7, 9 (odd numbers)range(10, 0, -1) → 10, 9, 8, 7, 6, 5, 4, 3, 2, 1 (countdown!)

All three formspython

print(list(range(5)))          # [0, 1, 2, 3, 4]
print(list(range(1, 6)))       # [1, 2, 3, 4, 5]
print(list(range(0, 10, 2)))   # [0, 2, 4, 6, 8]
print(list(range(10, 0, -1)))  # [10, 9, 8, 7, 6, 5, 4, 3, 2, 1]

🤔Quick Check

How many numbers does range(5) produce?

🤔Quick Check

What does list(range(2, 8, 2)) produce?

Practice Exercises

0/3 solved

Exercise 1 of 3easy

⏱ 00:00

Print a Range

Use list() and range() to print the numbers from 1 to 10 (inclusive).Expected output: [1, 2, 3, 4, 5, 6, 7, 8, 9, 10]

solution.py

1 / 3

Exercise 2 of 3easy

⏱ 00:00

Even Numbers

Print all even numbers from 0 to 20 using range() with a step.Expected output: [0, 2, 4, 6, 8, 10, 12, 14, 16, 18, 20]

solution.py

2 / 3

Exercise 3 of 3easy

⏱ 00:00

Countdown!

Print a countdown from 5 down to 1 using range() with a negative step.Expected output: [5, 4, 3, 2, 1]

solution.py

3 / 3

Solve all 3 exercises to unlock completion

Previous Next