Day 9/100: While Loops with Real-World Examples

Welcome to Day 9 of the 100 Days of Python series!
Today, we’ll explore the power of while loops — a tool that helps your program repeat actions until a certain condition is no longer true.

You’ll also see how while loops are used in real-world applications, from input validation to simple games.

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📦 What You'll Learn

• What a while loop is
• How to control repetition with conditions
• Using break and continue
• Real-world examples: password check, countdown, number guessing game

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🔁 What Is a while Loop?

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

🧠 Syntax:

while condition:
    # do something

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✅ Basic Example

count = 1

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

Output:

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

Once count becomes 6, the loop condition count <= 5 is no longer true, so the loop stops.

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🚫 Avoiding Infinite Loops

Make sure your loop condition will eventually be false — or you’ll create an infinite loop:

# ⚠️ This will run forever unless you stop it
while True:
    print("This goes on and on...")

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🛑 Using break to Exit a Loop

You can force-exit a loop using break.

while True:
    answer = input("Type 'exit' to stop: ")
    if answer == 'exit':
        print("Goodbye!")
        break

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⏭️ Using continue to Skip an Iteration

continue skips the rest of the loop for the current iteration and jumps to the next one.

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

Output:

1
2
4
5

(Notice how 3 is skipped)

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🔒 Real-World Example 1: Password Checker

correct_password = "python123"
attempts = 0

while attempts < 3:
    password = input("Enter password: ")
    if password == correct_password:
        print("Access granted.")
        break
    else:
        print("Wrong password.")
        attempts += 1

if attempts == 3:
    print("Too many attempts. Access denied.")

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⏳ Real-World Example 2: Countdown Timer

import time

countdown = 5
while countdown > 0:
    print(countdown)
    time.sleep(1)  # Pause for 1 second
    countdown -= 1

print("Time's up!")

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🎮 Real-World Example 3: Number Guessing Game

import random

number = random.randint(1, 10)
guess = 0

while guess != number:
    guess = int(input("Guess a number between 1 and 10: "))
    if guess < number:
        print("Too low!")
    elif guess > number:
        print("Too high!")
    else:
        print("Correct!")

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🧠 Recap

Today you learned:

• How to use while loops for repeating tasks
• How to use break to stop a loop early
• How to use continue to skip an iteration
• Real-world examples like login validation and guessing games

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