Loops

Question 1

What is the output of the following code?

count = 1
while count < 4:
count += 1
print(count, end = ‘ ‘)

Answer 1

2 3 4

Question 2

How many times will the following code print “Welcome to Python”?

count = 0
while count < 10:
    print("Welcome to Python")
    count += 1
 A. 8
 B. 9
 C. 10
 D. 11
 E. 0

Answer 2

C. 10

Hint: The count is initialized to 0 before the loop. The loop is executed 10 times for count from 1 to 9. When count is 10, the loop continuation condition becomes false. The loop is finished. So, the correct answer is C.

Question 3

What is the output of the following code?

x = 0
while x < 4:
x = x + 1

print("x is", x)
 A. x is 0
 B. x is 1
 C. x is 2
 D. x is 3
 E. x is 4

Answer 3

E. x is 4

Hint: x is 4 becasue x is incremented four times starting from 0.

Question 4

How many times will the following code print “Welcome to Python”?

count = 0
while count < 10:
    print("Welcome to Python")
 A. 8
 B. 9
 C. 10
 D. 11
 E. infinite number of times

Answer 4

E. infinite number of times

Question 5

What is the output of the following code?

count = 4
while count > 1:
count -= 1
print(count, end = ‘ ‘)

Answer 5

4 3 2

Question 6

How many times are the following loop bodies repeated? What is the printout of each loop?
(a)
i = 1
while i < 10:
    if i % 2 == 0:
        print(i)

(b)
i = 1
while i < 10:
    if i % 2 == 0:
    print(i)
    i += 1

(c)
i = 1
while i < 10:
    if i % 2 == 0:
        print(i)
    i += 1

Answer 6

(a) Infinite number of times.
(b) Infinite number of times.
(c) The loop body is executed nine times. The printout is 2, 4, 6, 8 on separate lines.

Question 7

Show the errors in the following code:
(a)
count = 0
while count < 100:
    print(count)

(b) 
count = 0
while count < 100:
print(count)
count -= 1

(c)
count = 0
while count < 100:
count += 1

Answer 7

(a) and (b) are infinite loops, (c) has an indentation error.

Question 8

What will be displayed when the following code is executed?

number = 6
while number > 0:
    number -= 3
    print(number, end = ' ')
 A. 6 3 0
 B. 6 3
 C. 3 0
 D. 3 0 -3
 E. 0 -3
Your answer B is incorrect Your answer is wrong The correct answer is C.
61.46% of users answered it correctly

Answer 8

C. 3 0

Hint: number is 6 before the loop. In the first iteration, number is reduced to 3. In the second iteration, number is reduced to 0. The loop is now finished. The loop body is executed 2 times for number 6 and 3. Since number is reduced by 3 before the print statement. 3 and 0 and displayed. So, the correct answer is C.Hint: number is 6 before the loop. In the first iteration, number is reduced to 3. In the second iteration, number is reduced to 0. The loop is now finished. The loop body is executed 2 times for number 6 and 3. Since number is reduced by 3 before the print statement. 3 and 0 and displayed. So, the correct answer is C.

Question 9

Can you convert any for loop to a while loop? List the advantages of using for loops.

Answer 9

Yes. The advantages of for loops are simplicity and readability. Compilers can produce more efficient code for the for loop than for the corresponding while loop.

Question 10

Convert the following for loop statement to a while loop:

sum = 0
for i in range(1001):
sum = sum + i

Answer 10

while loop:
sum = 0
i= 0
while i <= 1000:
    sum += i 
    i += 1

Question 11

Convert the following while loop into a for loop.
i = 1
sum = 0

while sum < 10000:
sum = sum + i
i += 1

Answer 11

sum = 0
for i in range(1, 10000):
if sum < 10000:
sum = sum + i

Question 12

Analyze the following statement:

sum = 0
for d in range(0, 10, 0.1):
sum += sum + d
A. The program has a syntax error because the range function cannot have three arguments.
B. The program has a syntax error because the arguments in the range must be integers.
C. The program runs in an infinite loop.
D. The program runs fine.

Answer 12

B. The program has a syntax error because the arguments in the range must be integers.

Question 13

Which of the following function is incorrect?
 A. range(0, 3.5)
 B. range(10, 4, -1)
 C. range(1, 3, 1)
 D. range(2.5, 4.5)
 E. range(1, 2.5, 4.5)

Answer 13

A. range(0, 3.5)
D. range(2.5, 4.5)
E. range(1, 2.5, 4.5)

Hint: The arguments in the range function must be integers.

Question 14

What is the output for y?

y = 0
for i in range(0, 10):
y += i

print(y)
 A. 10
 B. 11
 C. 12
 D. 13
 E. 45

Answer 14

E. 45

Hint: y should be 0 + 1 + 2 + 3 + 4 + 5 + 6 + 7 + 8 + 9 = 45v

Question 15

What is the output for y?

y = 0
for i in range(0, 10, 2):
y += i

print(y)
 A. 9
 B. 10
 C. 11
 D. 20
Your answer is correct Your answer is correct
79.24% of users answered it correctly

Hint: i is 0, 2, 4, 6, 8 What is the output for y?

y = 0
for i in range(0, 10, 2):
y += i

print(y)
 A. 9
 B. 10
 C. 11
 D. 20

Answer 15

D. 20

Hint: i is 0, 2, 4, 6, 8

Question 16

What is the output for y?

y = 0
for i in range(10, 1, -2):
y += i

print(y)
 A. 10
 B. 40
 C. 30
 D. 20

Answer 16

C. 30

Hint: i is 10, 8, 6, 4, 2, 0

Question 17

How many times is the print statement executed?

for i in range(10): 
    for j in range(i):
        print(i * j)
 A. 100
 B. 20
 C. 10
 D. 45

Answer 17

D. 45

Hint: The outer loop is executed 10 times for i from 0 to 9. For each i, the inner loop is executed i times. So, the println statement is executed 0 + 1 + 2 + … + 9 = 45 times.

Question 18

What is the keyword break for?

Answer 18

The keyword break is used to exit the current loop.

Question 19

What is the keyword continue for?

Answer 19

The keyword continue causes the rest of the loop body to be skipped for the current iteration.

Question 20

Will the following program terminate?

balance = 10

while True:
if balance < 9:
break
balance = balance - 9

A. Yes
B. No

Answer 20

A. Yes

Question 21

Will the following program terminate?

balance = 10

while True:
if balance < 9:
continue
balance = balance - 9

A. Yes
B. No

Answer 21

B. No

Question 22

What is sum after the following loop terminates?

sum = 0
item = 0
while item < 5:
    item += 1
    if sum >= 4:
        continue
    sum += item

print(sum)
 A. 5
 B. 6
 C. 7
 D. 8

Answer 22

B. 6

Hint: When sum >= 4, item is not added to sum.

Question 23

What is sum after the following loop terminates?

sum = 0
item = 0
while item < 5:
    item += 1
    sum += item
    if sum > 4:
        break

print(sum)
 A. 5
 B. 6
 C. 7
 D. 8

Answer 23

B. 6

Question 24

What will be displayed by after the following loop terminates?

number = 25
isPrime = True
i = 2 
while i < number and isPrime:
    if number % i == 0:
        isPrime = False

i += 1

print(“i is”, i, “isPrime is”, isPrime)

A. i is 5 isPrime is True
B. i is 5 isPrime is False
C. i is 6 isPrime is True
D. i is 6 isPrime is False

Answer 24

D. i is 6 isPrime is False

Hint: When i is 5, isPrime is assigned False, i += 1 is executed. So, i becomes 6. Now the loop ends since isPrime is False.

Question 25

What is the number of iterations in the following loop:

  for i in range(1, n + 1):
      # iteration

A. 2 * n
B. n
C. n - 1
D. n + 1

Answer 25

B. n

Hint: Since range(1, n + 1) returns a sequence of 1, 2, …, n. The number of iterations is n.

Question 26

Suppose the input for number is 9. What will be displayed by the following program?

number = int(input(“Enter an integer: “))

isPrime = True
for i in range(2, number):
if number % i == 0:
isPrime = False

print("i is", i)

    if isPrime:
        print(number, "is prime")
        break
    else:
        print(number, "is not prime")

A. i is 3 followed by 9 is prime
B. i is 3 followed by 9 is not prime
C. i is 2 followed by 9 is prime
D. i is 2 followed by 9 is not prime

Answer 26

C. i is 2 followed by 9 is prime

Question 27

A one-time execution of a loop body is referred to as an __________.

Answer 27

iteration of the loop

Question 28

There are two types of repetition statements: the ________ and the ________.

Answer 28

while loop and the for loop