Loops are a fundamental part of programming, allowing you to repeat a block of code as long as a condition is true. In Python, the while loop is one of two main loop types (the other is for).

This tutorial covers:

• How while loops work

• Syntax and flow

• Examples with explanations

• Controlling loops with break and continue

• Common pitfalls and best practices

• A complete example at the end

✅ What Is a while Loop?

A while loop repeats code as long as a condition remains true. It's useful when you don't know in advance how many times you'll need to loop.

Syntax

while condition:
    # code block

As long as condition is True, Python executes the code block.

Example 1: Basic Loop

count = 1

while count <= 5:
    print("Count:", count)
    count += 1

Output:

Count: 1
Count: 2
Count: 3
Count: 4
Count: 5

 count += 1 increases count each time, eventually making the condition False to stop the loop.

Example 2: Infinite Loop (Be Careful!)

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

This loop will never stop unless:

• You use break (see below)

• You interrupt it manually (Ctrl+C)

⛔ Breaking Out of a Loop – break

Use break to exit a loop early, even if the condition is still True.

while True:
    user_input = input("Enter 'q' to quit: ")
    if user_input == 'q':
        break
    print("You entered:", user_input)

Skipping Iterations – continue

Use continue to skip the current iteration and go to the next one.

x = 0

while x < 5:
    x += 1
    if x == 3:
        continue  # Skip printing 3
    print(x)

Output:

1
2
4
5

else Clause with while

The else block runs after the loop ends normally (not via break).

x = 0

while x < 3:
    print(x)
    x += 1
else:
    print("Loop finished without break.")

Common Patterns

Waiting for Correct Input

password = ""

while password != "admin123":
    password = input("Enter password: ")

print("Access granted")

Counting or Accumulating

total = 0
number = 1

while number <= 5:
    total += number
    number += 1

print("Sum:", total)

Common Pitfalls

Tips and Best Practices

• Use counters or variables to control the loop.

• Avoid infinite loops unless intentional.

• Use break sparingly to avoid unreadable logic.

• For known-length iteration, prefer a for loop.

• Keep conditions clear and simple.

Complete Example: Number Guessing Game

import random

secret_number = random.randint(1, 10)
guess = None

while guess != secret_number:
    guess = int(input("Guess a number (1-10): "))
    if guess < secret_number:
        print("Too low!")
    elif guess > secret_number:
        print("Too high!")

print("You guessed it!")

Summary Table

What's Next?

After learning while loops, explore:

• for loops for fixed iterations

• range() function

• Nested loops

• Using loops with lists, dictionaries, and files