Python While Loop

The while Loop in Python

The while loop is used to repeat a block of code as long as a specified condition is true. Unlike the for loop, which iterates over a sequence, the while loop focuses purely on the condition—it keeps looping until that condition becomes false.

Syntax of the while Loop

Here's the basic structure:

while condition:
    code_block

• condition: An expression that is evaluated before each iteration.
• code_block: The set of instructions that will run repeatedly as long as the condition is true.

A Simple Example

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

Output:

0
1
2
3
4

This loop prints numbers from 0 to 4. Each time through the loop, the condition count < 5 is checked. Once count reaches 5, the condition becomes false and the loop stops.

Infinite Loops

If the condition never becomes false, the loop will run forever. This is called an infinite loop.

while True:
    print("This will run forever!")

To stop an infinite loop during testing, you can use Ctrl + C or manually interrupt execution.

Breaking Out of a Loop

You can exit a while loop before the condition becomes false by using the break statement:

while True:
    user_input = input("Type 'exit' to stop: ")
    if user_input == "exit":
        break

Output (example):

Type 'exit' to stop: hello
Type 'exit' to stop: test
Type 'exit' to stop: exit

The loop ends only when the user types "exit".

Using continue to Skip Iterations

The continue statement skips the current iteration and goes back to re-check the condition:

count = 0
while count < 5:
    count += 1
    if count == 3:
        continue
    print(count)

Output:

1
2
4
5

The number 3 is skipped because continue causes the loop to immediately move to the next iteration.

Validating Input with while

A common use case for while is validating user input:

password = ""
while password != "secret":
    password = input("Enter the password: ")
print("Access granted")

This keeps asking the user for the correct password until they provide "secret".

The else Clause in while

Just like with for, a while loop can have an else clause. It runs only if the loop finishes normally (not interrupted by break):

x = 0
while x < 3:
    print(x)
    x += 1
else:
    print("Loop completed")

Output:

0
1
2
Loop completed

But if you break out of the loop:

x = 0
while x < 3:
    if x == 1:
        break
    print(x)
    x += 1
else:
    print("Loop completed")

Output:

0

The else block does not execute because the loop was interrupted.

Summary

• The while loop repeats code as long as a condition is true.
• Make sure the condition eventually becomes false—otherwise, you'll create an infinite loop.
• Use break to exit early, and continue to skip parts of the loop.
• The else clause runs if the loop completes normally.
• while is especially useful when you don’t know in advance how many times to repeat a task (like user input validation).

Use while when the repetition depends on dynamic conditions, not on fixed sequences.