Given the following assignment of a variable
LS = [1, 9, 2, 8, 3, 7, 5, 4]
What will be the output of the following?
print(LS[: :2] + LS[: :-2])

Correct option is D

The list LS is defined as:
LS = [1, 9, 2, 8, 3, 7, 5, 4]
The code LS[: :2] + LS[: :-2] performs the following operations:
1. LS[: :2]: This takes every second element from the list starting from index 0 (i.e., it selects every alternate element):
· The result is [1, 2, 3, 5] because we are picking every second element starting from the first element.
2. LS[: :-2]: This takes every second element from the list, but in reverse order (since the step is -2):
· The result is [4, 7, 8, 9] because we start from the last element (4) and move backward, picking every second element in reverse order.
When we concatenate these two slices (LS[: :2] + LS[: :-2]), the result is:
[1, 2, 3, 5] + [4, 7, 8, 9]
So, the final result is:
[1, 2, 3, 5, 4, 7, 8, 9]
Important Key Points:
1. Slicing: The [: :2] slice selects elements with a step of 2, starting from the first element.
2. Reverse Slicing: The [: :-2] slice selects elements with a step of -2, starting from the last element and moving backward.
3. Concatenation: The two slices are concatenated using the + operator, resulting in the combined list.
Knowledge Booster:
· Option (a): This is incorrect. The result does not match the expected output for either of the slices.
· Option (b): This is incorrect. The result of the concatenation doesn't match the expected sequence.
· Option (c): This is incorrect. The slices do not match the expected output.