How to Rotate a List in Python

Rotate a list to the right by k positions using Python's list slicing and modulo arithmetic.

Easy Python 3.9+ Aug 9, 2026 Lists & loops 15 views 0 copies

list rotation slicing modulo

Python code

11 lines
Python 3.9+
Run it 
def rotate_list_right(lst, k):
    if not lst:
        return lst
    k = k % len(lst)
    return lst[-k:] + lst[:-k] if k != 0 else lst


if __name__ == "__main__":
    sample = [1, 2, 3, 4, 5, 6, 7]
    for k in [0, 1, 3, 8, 20]:
        print(f"k={k}: {rotate_list_right(sample, k)}")

Output

stdout 
k=0: [1, 2, 3, 4, 5, 6, 7]
k=1: [7, 1, 2, 3, 4, 5, 6]
k=3: [5, 6, 7, 1, 2, 3, 4]
k=8: [7, 1, 2, 3, 4, 5, 6]
k=20: [1, 2, 3, 4, 5, 6, 7]

How it works

The key insight is using k % len(lst) to handle rotations larger than the list length, ensuring k is always within valid bounds. List slicing lst[-k:] takes the last k elements, while lst[:-k] takes the rest, and concatenating them produces the rotated list. The conditional checks if k is zero to return the original list, avoiding empty slice edge cases. This approach is O(n) in time and O(n) in space, making it efficient for most practical lists.

Common mistakes

  • Forgetting to handle empty lists with a guard clause, causing a ZeroDivisionError
  • Not using modulo when k exceeds list length, leading to incorrect rotations
  • Mutating the original list in-place when a new list is expected

Variations

  1. Use `collections.deque` with `rotate(k)` for in-place rotation
  2. Implement an in-place algorithm with reversal: reverse whole list, then reverse first k and last n-k parts

Real-world use cases

  • Scheduling tasks in a round-robin fashion by rotating a queue of worker IDs
  • Paging through a carousel of featured products by rotating a list of item keys
  • Implementing a circular buffer for rotating log files or sensor readings

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