Python Essentials 1 – Module 3 Test Answers

November 4, 2022 Python Essentials 1 Leave a comment

Python Essentials 1 – Module 3 Test Answers

PE1: Module 3. Boolean Values, Conditional Execution, Loops, Lists and List Processing, Logical and Bitwise Operations
1. An operator able to check whether two values are equal is coded as:

  • !=
  • =
  • ===
  • ==
Explanation: Remember that the == operator compares two arguments and checks if they are equal.

2. The value eventually assigned to x is equal to:

x = 1
x = x == x
  • False
  • True
  • 1
  • 0
Explanation: The == operator is more prominent in the operator hierarchy than the = operator. Therefore, the operation on the right is evaluated before the one on the left.

3. How many stars (*) will the following snippet send to the console?

i = 0
while i <= 3 :
    i += 2
    print("*")
  • zero
  • one
  • three
  • two
Explanation: Let’s analyze this example:

  • the i variable is assigned the integer value of 0,
  • the while loop compares if 0 <= 3, and since it is True, the loop is entered,
  • the i variable is incremented by 2, and a first star is printed on the console,
  • the while loop now compares if 2 <= 3, and since it is True, the loop is entered,
  • the variable i is incremented by 2, and a second star is printed on the console,
  • the while loop now compares if 4 <= 3, and since it is False, the loop is no longer executed.

4. How many stars (*) will the following snippet send to the console?

i = 0
while i <= 5 :
    i += 1
    if i % 2 == 0:
      break
    print("*")
  • two
  • one
  • three
  • zero
Explanation: Let’s analyze this example:

  • the i variable is assigned the integer value of 0,
  • the while
  • the i variable is incremented by 1, and its new value is 2,
  • the operation 1 % 2 is evaluated and returns 1,
  • the 1 is compared with 0, 1 == 0, and since it is False, the if conditional is not executed,
  • A star is printed on the console,
  • the while loop now compares if 2 <= 3, and since it is True, the loop is entered,
  • the i variable is incremented by 1, and its new value is 2,
  • the operation 2 % 2 is evaluated and returns 0,
  • the 0 is compared with 0, 0 == 0, and since it is True, the if conditional is executed,
  • the break statement is executed,
  • the while loop is terminated.

5. How many hashes (#) will the following snippet send to the console?

for i in range(1):
    print("#")
else:
    print("#")
  • two
  • three
  • one
  • zero
Explanation: Let’s analyze this example:

  • the for loop begins using the variable i as counter, it begins in 0 and stops before 1, so a single iteration is performed,
  • a first # is printed on the console,
  • after exiting the loop, the else statement is executed,
  • a second # is printed on the console.

6. How many hashes (#) will the following snippet send to the console?

var = 0
while var < 6:
    var += 1
    if var % 2 == 0:
        continue
    print("#")
  • two
  • three
  • zero
  • one
Explanation: Let’s analyze this example:

  • the var variable is assigned the integer value of 0,
  • the while loop begins comparing 0 < 6, and since it is True, the loop is entered,
  • the var variable is incremented by 1, and its new value is 1,
  • the operation 1 % 2 returns 1, and 1==0 returns False,
  • the if conditional is not executed,
  • a first # is printed in the console,
  • the while loop compares 1 < 6, and since it is True, the loop is entered,
  • the var variable is incremented by 1, and its new value is 2,
  • the operation 2 % 2 returns 0,, and 0==0 returns True,
  • the if conditional is executed, and the continue statement jumps to the while statement,
  • the while loop now compares 2 < 6, and since it is True, the loop is entered,
  • the var variable is incremented by 1, and its new value is 3,
  • the operation 3 % 2 returns 1, and 1==0 returns False,
  • the if conditional is not executed,
  • a second # is printed on the console,
  • the while loop compares 3 < 6, and since it is True, the loop is entered,
  • the var variable is incremented by 1, its new value is 4,
  • the operation 4 % 2 returns 0, and 0==0 returns True,
  • the if conditional is executed, and the continue statement jumps to the while statement,
  • the while loop now compares 4 < 6, and since it is True, the loop is entered,
  • the var variable is incremented by 1, and its new value is 5,
  • the operation 5 % 2 returns 1, and 1==0 returns False,
  • the if conditional is not executed,
  • a third # is printed on the console,
  • the while loop now compares 5 < 6, and since it is True, the loop is entered,
  • the var variable is incremented by 1, and its new value is 6,
  • the operation 6 % 2 returns 0, and 0==0 returns True,
  • the if conditional is executed, and the continue statement jumps to the while statement,
  • the while loop now compares 6 < 6, and since it is False, the loop is terminated.

7. How many hashes (#) will the following snippet send to the console?

var = 1
while var < 10:
    print("#")
    var = var << 1
  • one
  • four
  • eight
  • two
Explanation: Let’s analyze this example:

  • the var variable is assigned the integer value of 1,
  • the while loop begins comparing 1 < 10, and since it is True, the loop is entered,
  • a first # is printed on the console,
  • the var variable is binary shifted 1 position to the left, and it is now 2,
  • the while loop compares 2 < 10, and since it is True, the loop is entered,
  • a second # is printed on the console,
  • the var variable is binary shifted 1 position to the left, and it is now 4,
  • the while loop compares 4 < 10, and since it is True, the loop is entered,
  • a third # is printed on the console,
  • the var variable is binary shifted 1 position to the left, and it is now 8,
  • the while loop compares 8 < 10, and since it is True, the loop is terminated,
  • a fourth # is printed on the console,
  • the var variable is binary shifted 1 position to the left, and it is now 16,
  • the while loop compares 16 < 10, and since it is False, the loop is terminated.

8. What value will be assigned to the x variable?

z = 10
y = 0
x = y < z and z > y or y > z and z < y
  • True
  • False
  • 0
  • 1
Explanation: Let’s analyze this example:

  • the z variable is assigned the integer value of 10,
  • the y variable is assigned the integer value of 0,
  • the relational comparison y < z returns True,
  • the relational comparison z > y returns True,
  • the logical comparison True and True returns True,
  • the relational comparison y > z returns False,
  • the relational comparison z < y returns False,
  • the logical comparison False and False returns False,
  • finally, True or False returns True.

9. What is the output of the following snippet?

a = 1
b = 0
c = a & b
d = a | b
e = a ^ b
 
print(c + d + e)
  • 0
  • 1
  • 3
  • 2
Explanation: Let’s analyze this example:

  • the a variable is assigned the integer value of 1,
  • the b variable is assigned the integer value of 0,
  • the c variable is assigned the and bitwise result of a & b, which is 0,/li>
  • the d variable is assigned the or bitwise result of a | b, which is 1,
  • the e variable is assigned the xor bitwise result of a ^ b, which is 1,
  • the sum of the c,d and e variables is printed on the console, which is 2.

10. What is the output of the following snippet?

my_list = [3, 1, -2]
print(my_list[my_list[-1]])
  • 1
  • -2
  • 3
  • -1
Explanation: Let’s analyze this example:

  • the list my_list is created with the integer elements 3, 1, -2,
  • using a negative index (-1), the value of the last element in the list is obtained, which is -2,
  • -2 is used to obtain the value of the second last element, which is 1,
  • 1 is printed on the console.

11. What is the output of the following snippet?

my_list = [1, 2, 3, 4]
print(my_list[-3:-2])
  • []
  • [2, 3, 4]
  • [2]
  • [2, 3]
Explanation: Let’s analyze this example:

  • the list my_list is created with the integer elements 1, 2, 3, 4,
  • using negative indices (-3:-2), the elements from the third-last position to before the second-last position are selected,
  • the elements are printed on the console.

12. The second assignment:

vals = [0, 1, 2]
vals[0], vals[2] = vals[2], vals[0]
  • doesn't change the list
  • shortens the list
  • extends the list
  • reverses the list
Explanation: Let’s analyze this example:

  • the list vals is created with the integer elements 0,1,2,
  • using positive indices, the value in position 0 is swapped with the element in position 2,
  • the elements are now in this order: 2,1,0. Therefore, the list has been reversed.

13. After execution of the following snippet, the sum of all vals elements will be equal to:

vals = [0, 1, 2]
vals.insert(0, 1)
del vals[1]
  • 5
  • 4
  • 3
  • 2
Explanation: Let’s analyze this example:

  • the list vals is created with the integer elements 0, 1, 2,
  • using the insert method, an integer value of 1 is inserted in the first position of the list. The new list is 1,0,1,2,
  • using the del function, the element in position 1 is deleted, and the list is now 1,1,2,
  • the sum of the elements is 4.

14. Take a look at the snippet, and choose the true statements: (Select two answers)

nums = [1, 2, 3]
vals = nums
del vals[1:2]
  • nums and vals are of the same length
  • nums is longer than vals
  • nums and vals refer to the same list
  • nums is replicated and assigned to vals
Explanation: Remember that:

  • the assignment vals = nums does not create a new list, as vals is only another name for nums, and they both point to the same space in the memory,
  • if you delete any elements in vals, they are also deleted in nums.

15. Which of the following sentences are true? (Select two answers)

nums = [1, 2, 3]
vals = nums[-1:-2]
  • nums and vals are of the same length
  • vals is longer than nums
  • nums is longer than vals
  • nums and vals are two different lists
Explanation: Remember that:

  • when using indices, a new list is created with the elements specified within the brackets,
  • the new list created only has one element: [3].

16. What is the output of the following snippet?

my_list_1 = [1, 2, 3]
my_list_2 = []
for v in my_list_1:
    my_list_2.insert(0, v)
print(my_list_2)
  • [3, 2, 1]
  • [1, 2, 3]
  • [3, 3, 3]
  • [1, 1, 1]
Explanation: Let's analyze this code:

  • a list named my_list_1 is created with the elements 1,2,3,
  • an empty list named my_list_2 is created,
  • using a for loop, my_list_1 is iterated,
  • every element in my_list_1 is inserted in my_list_2, always in the position 0,
  • this is the list in each iteration:
    • [1]
    • [2,1]
    • [3,2,1]
  • finally, the list is printed on the console.

17. What is the output of the following snippet?

my_list = [1, 2, 3]
for v in range(len(my_list)):
    my_list.insert(1, my_list[v])
print(my_list)
  • [1, 2, 3, 3, 2, 1]
  • [3, 2, 1, 1, 2, 3]
  • [1, 1, 1, 1, 2, 3]
  • [1, 2, 3, 1, 2, 3]
Explanation: Let's analyze this code:

  • a list named my_list is created with the elements 1,2,3,
  • using a for loop in the range from 0 to the length of my_list minus 1, that is 0,1,2, the following elements are inserted in the list:
    • in iteration 1: the value of that returns my_list[0] is inserted in position 1. The list is now: [1,1,2,3]
    • in iteration 2: the value of that returns my_list[1] is inserted in position 1. The list is now: [1,1,1,2,3]
    • in iteration 3: the value of that returns my_list[2] is inserted in position 1. The list is now: [1,1,1,1,2,3]
    • finally, the list is printed on the console.

18. How many elements does the my_list list contain?

my_list = [i for i in range(-1, 2)]
  • three
  • one
  • two
  • four
Explanation: A list named my_list is created with a range of elements from -1 to an element before 2, that is: -1,0,1. Three elements

19. What is the output of the following snippet?

t = [[3-i for i in range (3)] for j in range (3)]
s = 0
for i in range(3):
    s += t[i][i]
print(s)
  • 7
  • 6
  • 4
  • 2
Explanation: Let's analyze this code:

  • a list named t is created with the following characteristics:
    • the first for loop iterates through 0,1,2, with these operations: 3-0, 3-1, 3-2. The results are added to the list: [3,2,1]
    • the second for loop also iterates through 0,1,2, performing the previous operation three times,
    • the resulting list is the following: [[3, 2, 1], [3, 2, 1], [3, 2, 1]]
  • the variable s is assigned the integer value of 0,
  • a third for loop iterates through 0,1,2,
  • the elements in positions [0][0], [1][1], [2][2] are added,
  • the result is 3+2+1 = 6,
  • the s variable is printed on the console.

20. What is the output of the following snippet?

my_list = [[0, 1, 2, 3] for i in range(2)]
print(my_list[2][0])
  • 0
  • 2
  • 1
  • the snippet will cause a runtime error
Explanation: Let's analyze this code:

  • a list named my_list is created with the element [0, 1, 2, 3] in the range of 0, 1 using a for loop. Therefore, the list created is as follows: [[0, 1, 2, 3], [0, 1, 2, 3]]
  • an attempt is made to access the element in position [2][0]
  • the index 2 is out of range, so the error message IndexError: list index out of range is generated.

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