Python while Loop – Comprehensive Guide with Examples

Python while Loop – Complete Guide with Examples

The while loop in Python is a fundamental control structure used to execute a block of code repeatedly as long as a given condition is True. It is particularly useful when the number of iterations is not known in advance.

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📌 Syntax of while Loop

while condition:
    # code block to execute repeatedly

Note: The condition is evaluated before each iteration. If it's True, the code block runs. If it's False, the loop ends.

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1️⃣ Example: Basic Counter

counter = 1
while counter <= 5:
    print("Counter is:", counter)
    counter += 1

Output:

Counter is: 1
Counter is: 2
Counter is: 3
Counter is: 4
Counter is: 5

🧠 Explanation:

• counter = 1 initializes the loop.
• counter <= 5 is the condition being checked.
• print() displays the current count.
• counter += 1 increases the value by 1 each loop.

🔔 Important: Always ensure that the condition eventually becomes false, or you’ll create an infinite loop!

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2️⃣ Example: while with User Input

password = ""
while password != "admin123":
    password = input("Enter password: ")
print("Access granted!")

Output:

Enter password: guest
Enter password: pass123
Enter password: admin123
Access granted!

🧠 Explanation:

• The loop runs until the user types admin123.
• input() reads user input during each iteration.

💡 Note: This is a basic way to create login-style checks using while loops.

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3️⃣ Example: Skipping Iteration with continue

i = 0
while i < 7:
    i += 1
    if i == 4:
        continue
    print("Number:", i)

Output:

Number: 1
Number: 2
Number: 3
Number: 5
Number: 6
Number: 7

⚠️ Caution: When i == 4, the continue skips the print statement and moves to the next iteration.

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4️⃣ Example: Stopping Loop Early with break

x = 10
while x > 0:
    print("Value:", x)
    if x == 6:
        break
    x -= 1

Output:

Value: 10
Value: 9
Value: 8
Value: 7
Value: 6

🧠 Explanation:

• When x becomes 6, break stops the loop immediately.

🔒 Note: Use break to exit loops when a condition is met, even if the main condition is still True.

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5️⃣ Example: Infinite Loop (⚠️ Use with Care)

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

Output: (runs until "exit" is typed)

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

⚠️ Caution: while True creates an infinite loop unless you add break to stop it.

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📋 Common Use Cases of while Loop

• Running code until user input is valid
• Creating loading screens or animations
• Game loops and server processes
• Polling or repeated checking of conditions

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🛠️ Example: Menu-Based Program

choice = ""
while choice != "3":
    print("\nMenu:")
    print("1. Say Hello")
    print("2. Show Info")
    print("3. Exit")
    choice = input("Choose an option: ")

    if choice == "1":
        print("Hello there!")
    elif choice == "2":
        print("Python is powerful.")
    elif choice == "3":
        print("Exiting...")
    else:
        print("Invalid choice.")

✅ Tip: You can use while loops to build simple interactive CLI apps like this.

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🔚 Summary

• while loop is used when the number of iterations is not known beforehand.
• Use break to exit early from a loop.
• Use continue to skip a particular iteration.
• Infinite loops should always have a breaking condition to avoid freezing the program.

💬 Practice Challenge: Write a program that asks users to guess a number between 1 and 10 using a while loop. Give hints like "Too low!" or "Too high!" until the correct number is guessed.

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🧪 Extra Practice Examples

Example: Print Even Numbers from 2 to 10

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

Example: Sum of Numbers Until 0 is Entered

total = 0
while True:
    n = int(input("Enter number (0 to stop): "))
    if n == 0:
        break
    total += n
print("Total sum:", total)

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📚 Practice Questions:

• ➤ Exercises

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📚 Related Topics:

• ➤ Python Arithmetic Operators
• ➤ Basic String Functions
• ➤ Advanced String Functions
• ➤ Basic List Functions
• ➤ Advanced List Functions : Part-1
• ➤ Advanced List Functions : Part-2
• ➤ Basic Tuple Functions
• ➤ Advanced Tuple Functions
• ➤ Basic Dictionary Functions
• ➤ Advanced Dictionary Functions
• ➤ Conditional Statements : if-elif-else
• ➤ Python 'for' Loop
• ➤ Python 'while' Loop
• ➤ Difference between 'for' loop and 'while' loop
• ➤ Introducing Python Functions

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