03-03: Exercises — while Loops¶

Notes reference: 03-03: while Loops

Q1: Basic while loop¶

Print the numbers 1 through 8 using a while loop.

Solution

i = 1
while i <= 8:
    print(i)
    i += 1

Q2: Sum until threshold¶

Add positive integers starting from 1 until the running total exceeds 50. Print the total and the last number added.

Solution

total = 0
n     = 1
while total <= 50:
    total += n
    n     += 1
print(f"Total: {total}, last number added: {n - 1}")
# Total: 55, last number added: 10

Q3: Validated input¶

Keep asking the user for an age until they enter a valid integer between 1 and 120.

Solution

age = -1
while not (1 <= age <= 120):
    try:
        age = int(input("Enter your age (1-120): "))
    except ValueError:
        print("Please enter a valid integer.")
print(f"Age recorded: {age}")

Q4: break — find first divisor¶

Find the smallest divisor of 91 greater than 1.

Solution

n = 91
i = 2
while i <= n:
    if n % i == 0:
        print(f"Smallest divisor of {n}: {i}")
        break
    i += 1
# Smallest divisor of 91: 7

Q5: continue — skip negatives¶

Given data = [3, -1, 7, -4, 0, 5, -2, 8], print only the positive values using a while loop.

Solution

data = [3, -1, 7, -4, 0, 5, -2, 8]
i    = 0
while i < len(data):
    if data[i] <= 0:
        i += 1
        continue
    print(data[i])
    i += 1
# 3 7 5 8

Q6: while/else¶

Check whether a number is prime using a while loop with an else clause.

Solution

n = int(input("Enter a number: "))
i = 2
while i * i <= n:
    if n % i == 0:
        print(f"{n} is NOT prime (divisible by {i})")
        break
    i += 1
else:
    print(f"{n} is prime")

Q7: Do-while simulation¶

Ask the user to enter a password. Keep asking until they enter "secure123". Print how many attempts it took.

Solution

attempts = 0
while True:
    password = input("Enter password: ")
    attempts += 1
    if password == "secure123":
        print(f"Access granted after {attempts} attempt(s).")
        break
    print("Wrong password, try again.")

Q8: for vs while — when to choose¶

Rewrite the following for loop as a while loop:

for i in range(0, 20, 3):
    print(i)

Solution

i = 0
while i < 20:
    print(i)
    i += 3

The for loop is preferred when the number of iterations is known. The while loop is preferred when iteration depends on a condition that changes unpredictably.

⬅️ Previous: 03-02: Exercises — for Loops ➡️ Next: 04-01: Exercises — Functions