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 = 1x = 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 = 0while 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 = 0while 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 = 0while 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 = 1while 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 = 10y = 0x = 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 = 1b = 0c = a & bd = a | be = 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 = numsdel 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 = 0for 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.
