🔁 Some Important Questions of While Loop in Python to Practice

Table of Contents

Let’s begin with the fundamentals of while loops — how they work, when to use them, and why beginners often make mistakes.

✅ Rule #1

While loop executes a block of code as long as the test condition is True.

✅ Rule #2

A control variable must be initialized before the loop starts, or the loop may not work.

✅ Rule #3

The condition is checked before executing the loop body — called an entry-controlled loop.

✅ Rule #4

You must update the variable inside the loop to avoid an infinite loop.

💡 Syntax:
while condition: # block of code

🔄 How Python While Loop Executes – Step-by-Step Flow

In Python, a while loop executes a block of code repeatedly until a specified condition becomes False. When the condition is no longer true, the program exits the loop and continues execution.

⚠️ Note: If the condition always remains True and never changes, the loop becomes an infinite loop — it will never stop unless you break it manually.

📊 Flowchart Explanation:

Start: The program begins execution.
Initialize variable: Set a value for your control variable (e.g., i = 0).
Check condition: Evaluate if the condition (i < 5) is true.
Execute loop body: Run the code block inside the loop.
Update variable: Change the value of the control variable (e.g., i += 1).
Repeat: Go back and recheck the condition.
Exit: When the condition becomes False, exit the loop.

✅ Example Flow

i = 1
while i <= 3:
    print("Number:", i)
    i += 1
# Output:
# Number: 1
# Number: 2
# Number: 3

🧪 Python While Loop Practice Questions – Top 10 Real Examples

Practice these real-world Python while loop programs to strengthen your fundamentals. These examples range from beginner to intermediate level, including sum, reverse, factorial, prime check, and more.

1️⃣ Print Numbers from 1 to 10 (with Breakdown)

count = 1
while count <= 10:
    print(count)
    count += 1

📤 Output:
1 2 3 4 5 6 7 8 9 10

2️⃣ Sum of First N Natural Numbers

n = 5
sum = 0
i = 1
while i <= n:
    sum += i
    i += 1
print("Sum =", sum)

📤 Output: Sum = 15

3️⃣ Prime Number Checker

num = 7
i = 2
flag = 0
while i < num:
    if num % i == 0:
        flag = 1
        break
    i += 1
if flag == 0:
    print(num, "is a prime number")
else:
    print(num, "is not a prime number")

📤 Output: 7 is a prime number

4️⃣ Print Message 3 Times

count = 0
while count < 3:
    print("Vista Academy Data Science Institute")
    count += 1

📤 Output:
Vista Academy Data Science Institute Vista Academy Data Science Institute Vista Academy Data Science Institute

5️⃣ Multiplication Table of a Number

number = 3
i = 1
while i <= 10:
    print(f"{number} x {i} = {number * i}")
    i += 1

📤 Output:
3 x 1 = 3 3 x 2 = 6 3 x 3 = 9 3 x 4 = 12 3 x 5 = 15 3 x 6 = 18 3 x 7 = 21 3 x 8 = 24 3 x 9 = 27 3 x 10 = 30

6️⃣ Reverse a Number

num = 1234
reverse = 0
while num > 0:
    digit = num % 10
    reverse = (reverse * 10) + digit
    num //= 10
print("Reversed number:", reverse)

📤 Output: Reversed number: 4321

7️⃣ Factorial Using While Loop

def factorial(n):
  if n < 0:
    return "Not defined"
  elif n == 0 or n == 1:
    return 1
  else:
    fact = 1
    i = 2
    while i <= n:
      fact *= i
      i += 1
    return fact

number = 5
print("Factorial:", factorial(number))

📤 Output: Factorial: 120

8️⃣ First 10 Prime Numbers

count = 0
num = 2
primes = []

while count < 10:
  is_prime = True
  i = 2
  while i*i <= num:
    if num % i == 0:
      is_prime = False
      break
    i += 1
  if is_prime:
    primes.append(num)
    count += 1
  num += 1

print("First 10 primes:", primes)

📤 Output: First 10 primes: [2, 3, 5, 7, 11, 13, 17, 19, 23, 29]

9️⃣ Display Even Numbers up to N

n = 10
i = 2
while i <= n:
    print(i)
    i += 2

📤 Output: 2 4 6 8 10

🔟 Sum of Digits of a Number

num = 456
sum = 0
while num > 0:
    digit = num % 10
    sum += digit
    num //= 10
print("Sum of digits:", sum)

📤 Output: Sum of digits: 15

1️⃣1️⃣ Find GCD of Two Numbers

a = 48
b = 18

while b != 0:
    a, b = b, a % b

print("GCD is:", a)

📤 Output: GCD is: 6

1️⃣2️⃣ Count Digits in a Number

num = 67891
count = 0

while num != 0:
    num //= 10
    count += 1

print("Total digits:", count)

📤 Output: Total digits: 5

1️⃣3️⃣ Check Armstrong Number

num = 153
temp = num
sum = 0

while temp > 0:
    digit = temp % 10
    sum += digit ** 3
    temp //= 10

if num == sum:
    print("Armstrong Number")
else:
    print("Not an Armstrong Number")

📤 Output: Armstrong Number

1️⃣4️⃣ Fibonacci Series (Up to N Terms)

n = 7
a, b = 0, 1
i = 0

while i < n:
    print(a, end=" ")
    a, b = b, a + b
    i += 1

📤 Output: 0 1 1 2 3 5 8

1️⃣5️⃣ Find Smallest Digit in a Number

num = 968421
smallest = 9

while num > 0:
    digit = num % 10
    if digit < smallest:
        smallest = digit
    num //= 10

print("Smallest digit:", smallest)

📤 Output: Smallest digit: 1

1️⃣6️⃣ Palindrome Number Check

num = 121
original = num
reverse = 0

while num > 0:
    digit = num % 10
    reverse = (reverse * 10) + digit
    num //= 10

if original == reverse:
    print("Palindrome Number")
else:
    print("Not a Palindrome")

📤 Output: Palindrome Number

1️⃣7️⃣ Print Alphabet Series A–Z

ch = 65
while ch <= 90:
    print(chr(ch), end=" ")
    ch += 1

📤 Output: A B C D E F G H I J K L M N O P Q R S T U V W X Y Z

1️⃣8️⃣ Find Power of a Number

base = 3
exp = 4
result = 1

while exp > 0:
    result *= base
    exp -= 1

print("Result:", result)

📤 Output: Result: 81

1️⃣9️⃣ Sum of Even Digits in a Number

num = 2846
sum = 0

while num > 0:
    digit = num % 10
    if digit % 2 == 0:
        sum += digit
    num //= 10

print("Sum of even digits:", sum)

📤 Output: Sum of even digits: 10

2️⃣0️⃣ Count Vowels in a String

text = "Data Science"
i = 0
count = 0

while i < len(text):
    if text[i].lower() in 'aeiou':
        count += 1
    i += 1

print("Total vowels:", count)

📤 Output: Total vowels: 5

🧠 Python While Loop – MCQ Quiz (Click to Answer)

Test your knowledge by selecting the correct answer. You’ll get instant feedback!

1️⃣ What will this code output?

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

🅐 1 2 3 4 5 🅑 1 2 3 4 🅒 1 2 3 🅓 0 1 2 3

✅ Correct! This prints numbers from 1 to 4.

2️⃣ A while loop will run:

🅐 Only once 🅑 A fixed number of times 🅒 Until a condition becomes False 🅓 Forever

✅ Correct! It runs until the condition is false.

3️⃣ What is the output?

x = 10
while x > 5:
    print(x)
    x -= 2

🅐 10 9 8 7 6 🅑 10 8 6 🅒 10 8 6 4 🅓 Infinite loop

✅ Correct! It prints 10, 8, 6 and stops.

4️⃣ What causes an infinite while loop?

🅐 A missing colon 🅑 Forgetting to update the condition variable 🅒 Using input() 🅓 All of the above

✅ Correct! Forgetting to change the variable keeps loop running forever.

5️⃣ What will be the last number printed?

i = 1
while i < 6:
    print(i)
    i += 1

🅐 5 🅑 6 🅒 1 🅓 0

✅ Correct! Last printed number is 5.

6️⃣ What will be the output?

i = 1
while i <= 3:
    print("Python")
    i += 1

🅐 Python Python 🅑 Python Python Python 🅒 Infinite loop 🅓 Nothing

✅ Correct! It prints "Python" three times.

7️⃣ Which of these while loops is infinite?

i = 10
while i >= 1:
    print(i)

🅐 No loop 🅑 i will become 0 🅒 Loop runs infinitely because i is never changed 🅓 Syntax Error

✅ Correct! It loops forever as i isn't updated.

8️⃣ What is the use of `break` in a while loop?

🅐 To skip the iteration 🅑 To exit the loop immediately 🅒 To pause the loop 🅓 To restart the loop

✅ Correct! break ends the loop execution instantly.

9️⃣ What does this loop print?

i = 0
while i < 3:
    print(i)
    i += 1

🅐 1 2 3 🅑 0 1 2 🅒 0 1 2 3 🅓 Nothing

✅ Correct! It prints 0, 1, 2 — then stops.

🔟 Which loop variable update causes an infinite loop?

x = 5
while x > 0:
    print(x)
    x = x + 1

🅐 No update 🅑 x = x - 1 🅒 x = x * 0 🅓 x = x + 1

✅ Correct! x increases, so the loop never ends.

1️⃣1️⃣ What will be the output?

x = 0
while x < 3:
    x += 1
    print(x * "*")

🅐 * * * 🅑 1 2 3 🅒 * ** *** 🅓 Nothing

✅ Correct! It prints increasing asterisks each time using string multiplication.

1️⃣2️⃣ What is the role of the condition in a while loop?

🅐 To create functions 🅑 To control when the loop should stop 🅒 To create variables 🅓 To end the program

✅ Yes! The while loop continues only as long as the condition remains True.

1️⃣3️⃣ What is the output of the following code?

i = 10
while i > 5:
    print(i, end=" ")
    i -= 2

🅐 10 8 6 🅑 5 6 7 🅒 10 9 8 7 6 🅓 Infinite loop

✅ Correct! It decreases by 2 until i becomes ≤ 5.

1️⃣4️⃣ Which statement exits a while loop immediately?

🅐 continue 🅑 break 🅒 exit() 🅓 pass

✅ Exactly! break exits the loop instantly.

1️⃣5️⃣ Which of the following creates an infinite loop?

🅐 while False: 🅑 while True: 🅒 while 0: 🅓 while x == 5 (when x = 3)

✅ Great! while True: runs forever unless a break condition is included.

1️⃣6️⃣ What will be the output?

x = 5
while x > 0:
    print(x, end=" ")
    x -= 1

🅐 5 4 3 2 1 🅑 1 2 3 4 5 🅒 0 1 2 3 4 🅓 5 4 3 2 1 0

✅ Correct! Loop prints and decrements x until it becomes 0.

1️⃣7️⃣ What happens if a while loop has no terminating condition?

🅐 The program ends immediately 🅑 It runs infinitely 🅒 It runs once 🅓 Syntax error occurs

✅ Right! Without a false condition, while loop goes on forever.

1️⃣8️⃣ Which keyword is used to skip current loop iteration?

🅐 continue 🅑 skip 🅒 break 🅓 stop

✅ Perfect! continue skips to the next loop iteration.

1️⃣9️⃣ What is the output?

i = 1
while i <= 5:
    print(i**2)
    i += 1

🅐 1 2 3 4 5 🅑 1 4 9 🅒 1 4 9 16 25 🅓 2 4 6 8 10

✅ Correct! It prints the square of each number from 1 to 5.

2️⃣0️⃣ Which of the following can cause a while loop to become infinite unintentionally?

🅐 A break inside the loop 🅑 A missing update to the loop variable 🅒 Proper condition 🅓 Using input()

✅ Yes! If the loop variable is not updated, it may never terminate.

❓ FAQs: While Loop in Python for Beginners

🔄 What is a while loop in Python?

A while loop is a control flow statement that repeatedly executes a block of code as long as the given condition is True.

🛑 What is an indefinite or infinite while loop?

An infinite while loop runs endlessly because the condition never becomes False. For example: while True: will run forever unless stopped by a break statement.

🔁 How to avoid infinite loops in Python?

Always make sure the condition inside your while loop can eventually become False. Update your loop variable inside the loop to avoid infinite repetition.

🧠 Can we use else with while loop in Python?

Yes! Python allows using an else block with while loop, which runs only when the condition becomes False naturally (not interrupted by break).

🔢 How to count iterations in a while loop?

You can use a counter variable (like i = 0) and increment it on each iteration to track how many times the loop runs.

⚠️ What are common mistakes in while loop?

– Forgetting to update the loop variable
– Wrong indentation
– Using = instead of ==
– Creating an infinite loop accidentally

🧪 Can I use continue and break in a while loop?

Yes, break is used to exit the loop early, and continue is used to skip the current iteration and move to the next one.

📌 What is the syntax of a while loop in Python?

while condition:
statement(s)
Example:
i = 1 while i <= 5: print(i) i += 1

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