Python program to remove rows with duplicate element in Matrix

When it is required to remove rows with duplicate elements in a matrix, a list comprehension and the set operator is used to filter out rows containing duplicate values.

Understanding the Problem

A matrix (list of lists) may contain rows where elements are repeated. We need to identify and remove such rows, keeping only those with unique elements ?

# Example matrix with some rows having duplicate elements
matrix = [[34, 23, 34], [17, 46, 47], [22, 14, 22], [28, 91, 19]]

print("Original matrix:")
for i, row in enumerate(matrix):
    print(f"Row {i}: {row}")

Original matrix:
Row 0: [34, 23, 34]
Row 1: [17, 46, 47]
Row 2: [22, 14, 22]
Row 3: [28, 91, 19]

Method 1: Using List Comprehension with set()

We can use a list comprehension that compares the length of a set (unique elements) with the original row length ?

matrix = [[34, 23, 34], [17, 46, 47], [22, 14, 22], [28, 91, 19]]

print("The original matrix is:")
print(matrix)

# Remove rows with duplicate elements
filtered_matrix = [row for row in matrix if len(set(row)) == len(row)]

print("The matrix after removing rows with duplicates:")
print(filtered_matrix)

The original matrix is:
[[34, 23, 34], [17, 46, 47], [22, 14, 22], [28, 91, 19]]
The matrix after removing rows with duplicates:
[[17, 46, 47], [28, 91, 19]]

Method 2: Using Filter Function

Alternatively, we can use the filter() function with a lambda expression ?

matrix = [[34, 23, 34], [17, 46, 47], [22, 14, 22], [28, 91, 19]]

print("Original matrix:")
print(matrix)

# Using filter with lambda
filtered_matrix = list(filter(lambda row: len(set(row)) == len(row), matrix))

print("Filtered matrix:")
print(filtered_matrix)

Original matrix:
[[34, 23, 34], [17, 46, 47], [22, 14, 22], [28, 91, 19]]
Filtered matrix:
[[17, 46, 47], [28, 91, 19]]

How It Works

The solution works by comparing two lengths:

• len(set(row)) − Length of unique elements in the row

• len(row) − Total length of the row

• If both lengths are equal, the row has no duplicates

• If lengths differ, the row contains duplicate elements and is excluded

Example with Different Data Types

This method works with different data types as well ?

mixed_matrix = [['a', 'b', 'a'], [1, 2, 3], ['x', 'y', 'z'], [5, 5, 6]]

print("Mixed data type matrix:")
print(mixed_matrix)

result = [row for row in mixed_matrix if len(set(row)) == len(row)]

print("Rows without duplicates:")
print(result)

Mixed data type matrix:
[['a', 'b', 'a'], [1, 2, 3], ['x', 'y', 'z'], [5, 5, 6]]
Rows without duplicates:
[[1, 2, 3], ['x', 'y', 'z']]

Conclusion

Use list comprehension with set() to efficiently remove matrix rows containing duplicate elements. The len(set(row)) == len(row) condition identifies rows with unique elements only.