What's the Most Efficient Way to Rotate a List in Python?

Efficient List Rotation in Python

When rotating a list, the standard approach is to slice the list at the desired rotation point and recombine the resulting segments. However, there are more efficient options available.

Using a Collections.deque

The Python standard library provides the collections.deque data structure, optimized for operations at both ends of the list. It features a dedicated rotate() method for efficient list rotation.

Consider the following code:

from collections import deque

items = deque([1, 2, 3])
items.rotate(1)  # Rotate the deque to the right by 1 position
print(items)  # Output: deque([3, 1, 2])

This method offers significant performance advantages over the standard slicing technique, especially for larger lists.

Using Rotate Algorithms

Alternatively, specialized algorithms exist for list rotation. One such algorithm is the cyclic rotation, which involves repeatedly swapping the first and last elements of the list.

Here's an implementation in Python:

def cyclic_rotate(lst, n):
    """Rotates the list by n positions."""
    n = n % len(lst)
    for i in range(n):
        lst[0], lst[-1] = lst[-1], lst[0]
    return lst

This algorithm performs constant time swaps and is suitable for smaller lists or when the rotation factor is known in advance.

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