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While Loop in Python

  • This lesson teaches how the while loop works in Python and how to execute code repeatedly based on a condition.

  • What is a while Loop?

    The while loop in Python is used to repeat a block of code as long as a given condition is True.

    👉 The loop continues until the condition becomes False.

    Why Use a while Loop?

    We use a while loop when:

    • The number of repetitions is not known in advance

    • Repetition depends on a condition

    • Continuous checking is required

    • Programs involve user input, validation, or retry logic

    Syntax of while Loop

    Basic Syntax

    while condition:

        statement(s)


    🔹 Syntax Explanation

    Part

    Description

    while

    Loop keyword

    condition

    Boolean expression

    :

    Start of loop block

    Indentation

    Defines loop body

    Update

    Required to avoid infinite loop



    Flow of Execution (while Loop)

    1. Condition is checked

    2. If True → loop body executes

    3. Variable is updated

    4. Condition is checked again

    5. Loop ends when condition becomes False

Printing Numbers Using while Loop

This program prints numbers from 1 to 5 using a while loop. 

count = 1

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

  • Infinite Loop 

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

while True:
    print("Hello")
Note:

Always update the condition variable.

  • What is else in while Loop?

    The else block in a while loop executes:

    • ✅ When the loop ends normally

    • ❌ Not executed if the loop stops using break

    👉 Same rule as for-else.



    Syntax of while-else

    while condition:

        statement(s)

    else:

        statement(s)


Using else with while Loop (No break)

This program shows that the else block executes when the loop completes normally. 

num = 1

while num <= 3:
    print(num)
    num += 1
else:
    print("Loop finished successfully")

Using else with while Loop and break

This program demonstrates that the else block is skipped when break is used. 

num = 1
while num <= 5:
    if num == 3:
        break
    print(num)
    num += 1
else:
    print("Loop completed")

  • Where while-else is Used?

    • Retry mechanisms

    • Login systems

    • Search operations

    • Validation logic

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