Python - Column deletion from list of lists

In a list of lists, an element at the same index of each sublist represents a column-like structure. In this article we will see how to delete a column from a list of lists, which means deleting the element at the same index position from each sublist.

Using pop() Method

The pop() method removes and returns the element at a specific index. We can use list comprehension to apply pop() to each sublist ?

# List of lists representing tabular data
data = [[3, 9, 5, 1],
        [4, 6, 1, 2],
        [1, 6, 12, 18]]

print("Original list:")
print(data)

# Remove column at index 2 using pop()
[row.pop(2) for row in data]

print("\nAfter deleting column at index 2:")
print(data)

Original list:
[[3, 9, 5, 1], [4, 6, 1, 2], [1, 6, 12, 18]]

After deleting column at index 2:
[[3, 9, 1], [4, 6, 2], [1, 6, 18]]

Using del Statement

The del statement directly removes an element at the specified index without returning it. This approach uses a for loop to iterate through each sublist ?

# List of lists representing tabular data
data = [[3, 9, 5, 1],
        [4, 6, 1, 2],
        [1, 6, 12, 18]]

print("Original list:")
print(data)

# Remove column at index 2 using del
for row in data:
    del row[2]

print("\nAfter deleting column at index 2:")
print(data)

Original list:
[[3, 9, 5, 1], [4, 6, 1, 2], [1, 6, 12, 18]]

After deleting column at index 2:
[[3, 9, 1], [4, 6, 2], [1, 6, 18]]

Using List Comprehension with Slicing

This approach creates a new list by excluding the specified column index, preserving the original data ?

# List of lists representing tabular data
data = [[3, 9, 5, 1],
        [4, 6, 1, 2],
        [1, 6, 12, 18]]

print("Original list:")
print(data)

# Create new list excluding column at index 2
column_to_delete = 2
result = [row[:column_to_delete] + row[column_to_delete + 1:] for row in data]

print(f"\nAfter removing column at index {column_to_delete}:")
print(result)
print(f"\nOriginal data unchanged:")
print(data)

Original list:
[[3, 9, 5, 1], [4, 6, 1, 2], [1, 6, 12, 18]]

After removing column at index 2:
[[3, 9, 1], [4, 6, 2], [1, 6, 18]]

Original data unchanged:
[[3, 9, 5, 1], [4, 6, 1, 2], [1, 6, 12, 18]]

Comparison

Conclusion

Use pop() when you need the deleted values, del for simple in-place deletion, or list comprehension to preserve the original data. All methods effectively remove columns from list of lists.