Lecture-27 2d List_Operations 2024-25

COMP101 Introduction to Programming 2024-25 Lecture-27

2-D List Processing

Page 1

• Lecture focus: 2-D list processing

• Course: COMP101 Introduction to Programming

• Year: 2024-25

• Lecture: 27

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Function for List Initialization

• Function Definition: def list_init(data, num_rows, num_cols)

  • Parameters:

    • data: Value to fill the list

    • num_rows: Number of rows in the list

    • num_cols: Number of columns in the list

  • List Comprehension:

    • Creates a 2-D list initialized with 'data'

    • Syntax: return [[data for i in range(num_rows)] for j in range(num_cols)]

• Example Use in main() Function:

  • Call to function: unity_matrix = list_init(1, 4, 4)

  • Output:

    • print(unity_matrix)

    • Result:

    • [[1, 1, 1, 1], [1, 1, 1, 1], [1, 1, 1, 1], [1, 1, 1, 1]]

Summary

• Creates a unity matrix (4x4) filled with 1's.

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Random Initialization of a 3x3 List

• Import random: Enables random number generation

• Matrix Definition:

  • row = 3, col = 3

  • Initializing a 3x3 matrix with zeros:

  • list_3x3 = [[0,0,0],[0,0,0],[0,0,0]]

• Randomization Loop:

  • Uses nested loops to fill the matrix

  • Code Explanation:

    • for r in range(row):

    • for c in range(col):

    • list_3x3[r][c] = random.randint(1, 4)

• Example Output:

  • Example of a possible output:

  • [[2, 4, 4], [1, 2, 3], [3, 4, 1]]

Summary

• Randomly fills a 3x3 list with integers between 1 to 4.

Page 4

Summing Values in a 2-D List

• Initialization:

  • sum = 0

  • Example 2-D list: list_2x3 = [[1,2,3],[4,5]]

• Nested Loop for Summation:

  • for row in list_2x3:

  • for col in row:

    • Adds each element to sum

• Code Example:

  • `print(