while loop

What does a while loop do?

• Runs code once

• Runs code until a condition becomes False

• Runs only with numbers

• Runs forever

Answer explanation

A while loop repeatedly executes a block of code as long as a specified condition remains true. It stops running when the condition evaluates to false, making 'Runs code until a condition becomes False' the correct choice.

What is the output of this code?

i = 1

while i <= 3:

print(i) i += 1

• 1 1 1

• 1 2 3

• 1 2 3 4

• Error

Answer explanation

The code initializes i to 1 and enters a while loop that runs as long as i is less than or equal to 3. It prints the value of i and increments it by 1 each time. The output is 1, 2, 3, which corresponds to the correct choice.

What happens if the condition in while is always True?

• Runs once

• Infinite loop

• Skips the loop

• Gives error

Answer explanation

If the condition in a while loop is always true, the loop will continue to execute indefinitely, resulting in an infinite loop. This means the program will not exit the loop unless interrupted or terminated.

Which of these can cause an infinite loop?

• Missing print()

• No indentation

• No i += 1

• Using if

Answer explanation

The correct choice is 'No i += 1'. Without this increment, the loop variable 'i' never changes, causing the loop to run indefinitely. The other options do not directly lead to an infinite loop.

How many times will this loop run?

i = 1

while i < 5:

i += 1

• 4

• 5

• 0

• Infinite

Answer explanation

The loop starts with i = 1 and runs while i < 5. It increments i by 1 each time. The values of i will be 1, 2, 3, 4, and then it stops when i becomes 5. Thus, the loop runs 4 times, making the correct answer 4.

What does this program do?

x = 1

while x <= 5:

print("Hi")

x += 1

• Prints Hi 4 times
  

• Prints Hi 5 times

• Runs forever

• Gives error

Answer explanation

The program initializes x to 1 and enters a loop that runs while x is less than or equal to 5. It prints 'Hi' and increments x by 1 each time, resulting in 'Hi' being printed 5 times before the loop ends.

Which keyword is used to exit a while loop early?

• stop

• exit

• break

• return

Answer explanation

The keyword 'break' is used to exit a while loop early. It immediately terminates the loop, allowing the program to continue with the next statement following the loop. Other options like 'stop' and 'exit' are not valid in this context.

What is the output?

i = 3

while i > 0:

print(i)

i -= 1

• 1 2 3

• 3 2 1

• 3 3 3

• 0 1 2

Answer explanation

The loop starts with i = 3. It prints i, then decrements i by 1. This continues until i is no longer greater than 0. The output is 3, 2, 1, which matches the correct answer choice.

What is the use of i += 1 in a loop?

• It ends the loop

• It increases loop variable

• It prints i

• It starts the loop

Answer explanation

The expression i += 1 increments the loop variable i by 1 in each iteration. This is essential for controlling the loop's execution and preventing infinite loops, making 'It increases loop variable' the correct choice.

What does this loop do?

num = 1

while num <= 10:

print(num)

num += 2

• Prints 1 to 10

• Prints even numbers

• Prints 1, 3, 5, 7, 9

• Error

Answer explanation

The loop starts with num = 1 and increments by 2 each iteration. It prints num while it is less than or equal to 10, resulting in the output: 1, 3, 5, 7, 9. Thus, the correct choice is 'Prints 1, 3, 5, 7, 9'.