Python While Loop

A while loop executes a block of code as long as a condition is True.

The loop continues running until the condition becomes False.

Syntax

while condition:
    # code block

Simple While Loop

Example:

i = 1

while i <= 5:
    print(i)
    i += 1

Output:

1
2
3
4
5

How It Works

1. Check the condition.
2. If the condition is True, execute the code block.
3. Return to the condition.
4. Repeat until the condition becomes False.

Example:

count = 1

while count <= 3:
    print("Hello")
    count += 1

Output:

Hello
Hello
Hello

The Increment Operator

Remember to update the loop variable, otherwise the loop will run forever.

Example:

i = 1

while i <= 5:
    print(i)
    i += 1

Infinite Loop

If the condition never becomes False, the loop runs forever.

Example:

i = 1

while i <= 5:
    print(i)

This creates an infinite loop because i is never updated.

Break Statement

The break statement stops the loop immediately.

Example:

i = 1

while i <= 10:
    print(i)

    if i == 5:
        break

    i += 1

Output:

1
2
3
4
5

Continue Statement

The continue statement skips the current iteration and moves to the next one.

Example:

i = 0

while i < 5:
    i += 1

    if i == 3:
        continue

    print(i)

Output:

1
2
4
5

Else Statement

The else block executes when the loop finishes normally.

Example:

i = 1

while i <= 3:
    print(i)
    i += 1
else:
    print("Loop Finished")

Output:

1
2
3
Loop Finished

Using User Input

Example:

password = ""

while password != "admin":
    password = input("Enter Password: ")

print("Access Granted")

Nested While Loop

A while loop can be placed inside another while loop.

Example:

i = 1

while i <= 3:
    j = 1

    while j <= 2:
        print(i, j)
        j += 1

    i += 1

Output:

1 1
1 2
2 1
2 2
3 1
3 2

Practical Example

Print the first 5 even numbers.

Example:

num = 2

while num <= 10:
    print(num)
    num += 2

Output:

2
4
6
8
10

Summary

• A while loop repeats code while a condition is True.
• The condition is checked before each iteration.
• Update the loop variable to avoid infinite loops.
• Use break to exit a loop.
• Use continue to skip an iteration.
• Use else to execute code when the loop ends normally.
• while loops are useful when the number of iterations is unknown.