Python while Loop Tutorial for Beginners

A while loop repeats code as long as a condition stays true. Press Play and watch the check happen before every round.

How a while loop works

Python checks the condition. If it is TRUE, the body runs and Python goes back to check again. When it becomes FALSE, the loop ends.

n = 3
while n > 0:
    print(n)
    n = n - 1
print("Go!")

Output: 3, 2, 1, then Go!.

for vs while

Use for when you know how many items to go through. Use while when you repeat until something happens, like a correct password or a counter reaching zero.

Stopping early with break

while True:
    word = input("Type quit: ")
    if word == "quit":
        break

Common beginner mistakes

Forgetting to change the variable, creating an infinite loop.
Writing the condition the wrong way round (n < 0 instead of n > 0).

Practice exercises

Try each one yourself first, then open it in the Visualizer to watch every line run.

Exercise 1

Countdown

Count down from 5 to 1, then print "Lift off!".

n = 5
# while loop here

Try it in the Visualizer

Hint

Print n, then reduce it by 1 inside the loop.

Show solution and explanation

n = 5
while n > 0:
    print(n)
    n = n - 1
print("Lift off!")

The condition is checked before every round. When n reaches 0, n > 0 is False and the loop ends. Without n = n - 1 it would never stop.

Watch the solution step by step

Exercise 2

Sum until a limit

Add 1 + 2 + 3 + … and stop as soon as the total is more than 20. Print how many numbers you added.

total = 0
count = 0
# keep adding while total <= 20

Try it in the Visualizer

Hint

Increase count first, then add count to total.

Show solution and explanation

total = 0
count = 0
while total <= 20:
    count = count + 1
    total = total + count
print(count, total)  # 6 21

Watch both variables in memory: after 6 rounds total is 21, the condition 21 <= 20 is False, and the loop ends.

Watch the solution step by step

Exercise 3

Find the first multiple

Find the first number from 1 upward that is divisible by both 4 and 6, using break.

n = 1
while True:
    # stop when n fits both
    n = n + 1
print(n)

Try it in the Visualizer

Hint

Use if n % 4 == 0 and n % 6 == 0: break — before increasing n.

Show solution and explanation

n = 1
while True:
    if n % 4 == 0 and n % 6 == 0:
        break
    n = n + 1
print(n)  # 12

while True repeats forever, so break is the only exit. At n = 12 both remainders are 0 and break jumps straight to print.

Watch the solution step by step

Python while Loop — Explained Visually

Python code

Variables / Memory

Execution

Output

Flow chart

How a while loop works

for vs while

Stopping early with break

Common beginner mistakes

Practice exercises

Countdown

Sum until a limit

Find the first multiple

Try your own code