PCEP Practice Test: Lists in Lists - Matrices and Cubes

Question 1: What is a matrix in Python?

1. A list with multiple data types
2. A list containing other lists as elements
3. A function for generating numbers
4. A method to sort lists

Question 2: How do you access the element in the second row and third column of a 2D list named matrix?

matrix = [[1, 2, 3], [4, 5, 6], [7, 8, 9]]

1. matrix[1][2]
2. matrix[2][1]
3. matrix[3][2]
4. matrix[1, 2]

Question 3: What is the correct way to initialize a 3x3 matrix with all zeroes?

1. matrix = [[0 for i in range(3)] for j in range(3)]
2. matrix = [[0, 0, 0], [0, 0, 0], [0, 0, 0]]
3. matrix = [[0] * 3 for i in range(3)]
4. All of the above

Question 4: Which of the following are valid ways to access elements in a 2D list? (Choose all that apply)

1. matrix[1][2]
2. matrix[0][0]
3. matrix[2, 1]
4. matrix[1]

Question 5: Which of the following code snippets correctly create a 2x2 matrix? (Choose two)

1. matrix = [[1, 2], [3, 4]]
2. matrix = [1, 2, 3, 4]
3. matrix = [[1, 2], [3, 4], [5, 6]]
4. matrix = [[1, 2], [3, 4]] * 2

Question 6: A 3D list in Python can be thought of as a __________ of 2D matrices.

Question 7: The expression cube[1][2][0] accesses an element from a __________ list.

Question 8: Arrange the following code statements in the correct order to create a 3x3 identity matrix:

1. identity_matrix = [[0, 0, 0], [0, 1, 0], [0, 0, 1]]
2. print(identity_matrix)
3. identity_matrix = [[1 if i == j else 0 for j in range(3)] for i in range(3)]

Question 9: Arrange the following code snippets in the correct order to initialize a 2x2x2 cube with all elements set to 1:

1. print(cube)
2. cube = [[[1 for k in range(2)] for j in range(2)] for i in range(2)]

Question 10: Complete the code to create a 4x4 matrix with all elements set to 7:

matrix = [[__________ for j in range(4)] for i in range(4)]

Question 11: Complete the code to create a 2x2 matrix using nested list comprehensions:

matrix = [[__________] for i in range(2)]

Question 12: Insert the correct code to create a 3D list (2x2x2 cube) with all elements initialized to 0:

cube = __________

Question 13: Insert the correct code to access the element in the third row and second column of a 4x4 matrix named matrix:

element = __________

Question 14: Rearrange the code to create a 3x3 matrix where each element is the sum of its row and column indices:

1. print(matrix)
2. for i in range(3):
3. matrix = [[i + j for j in range(3)] for i in range(3)]

Question 15: Organize the steps to initialize a 4x4 matrix with each element set to its row index:

1. print(matrix)
2. matrix = [[i for j in range(4)] for i in range(4)]

Question 16: What does the following code output?

matrix = [[1, 2, 3], [4, 5, 6], [7, 8, 9]]
print(matrix[2][0])

1. 1
2. 7
3. 3
4. 3

17. What does the following code output?

cube = [[[1 for k in range(2)] for j in range(2)] for i in range(2)]
print(cube[1][0][1])

1. 1
2. 0
3. 2
4. None

Question 18: A 2D list in Python is represented as a list containing other lists.

1. True
2. False

Question 19: Accessing an element in a 3D list requires three levels of indexing.

1. True
2. False

Question 20: What happens if you try to access an element that is out of bounds in a matrix?

1. It returns None
2. It raises an IndexError
3. It returns an empty list
4. It raises a TypeError

Question 21: Which of the following statements about matrices and cubes is correct?

1. A matrix can only have numeric data.
2. A cube is a 3D list, with lists nested three levels deep.
3. List comprehensions cannot be used to generate matrices.
4. Python does not support matrices or cubes natively.

Question 22: Which of the following expressions correctly creates a 2x3 matrix?

1. [[1, 2, 3] for _ in range(2)]
2. [[1, 2] for _ in range(3)]
3. [[1, 2, 3]] * 2
4. [[1, 2, 3, 4] for _ in range(2)]

Question 23: A 3D list can be visualized as a __________ of 2D matrices.

Question 24: The expression matrix[1][2] accesses the element in the second __________ and third column of the matrix.

Question 25: What is the output of the following code?

matrix = [[10, 20], [30, 40]]
print(matrix[1][1])

1. 10
2. 20
3. 30
4. 40