Python - Retain all K elements Rows

Python - Retain all K elements Rows

In this tutorial, we'll be learning how to retain rows from a matrix (list of lists) where all elements are equal to a specified value K. If any row doesn't satisfy this criterion, it will be removed from the resulting matrix.

Objective:

Given a matrix data and a number k, filter out the rows where all elements are not equal to k.

Sample Input:

data = [ [3, 3, 3], [3, 4, 3], [2, 2, 2], [3, 3, 3] ] k = 3

Expected Output:

[ [3, 3, 3], [3, 3, 3] ]

Tutorial:

Step 1: Define a function that checks if all elements of a given list are equal to a value k.

def all_elements_are_k(lst, k): return all(elem == k for elem in lst)

Step 2: Use a list comprehension to filter out rows in the matrix that don't have all elements equal to k.

def retain_rows_with_k(data, k): return [row for row in data if all_elements_are_k(row, k)]

Step 3: Test the function with the sample input.

data = [ [3, 3, 3], [3, 4, 3], [2, 2, 2], [3, 3, 3] ] k = 3 print(retain_rows_with_k(data, k)) # Output: [[3, 3, 3], [3, 3, 3]]

Additional Points:

  1. Performance: The solution operates in O(n*m) time complexity, where n is the number of rows and m is the number of columns in the matrix. This is because we traverse each row once, and for each row, we check all its elements.

  2. Flexibility: This method can easily be adjusted to work with different conditions. For example, if you want to retain rows where all elements are not equal to k, you can simply invert the condition in the all_elements_are_k function.

Recap:

In this tutorial, we learned how to retain rows from a matrix (list of lists) where all elements match a specified value k in Python. This can be particularly useful when filtering data or working with matrices that need to meet certain criteria.

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