Coding Task: Reverse a List In-Place (Python)

Context

You're implementing a utility function during a technical screen. The function must reverse a Python list in-place without allocating another list.

Requirements

• Implement a function that reverses a Python list in-place.
• Constraints:
  1. No slicing (e.g., arr[::-1]), no list(), and no reversed().
  2. Time complexity: O(n).
  3. Extra space: O(1).
  4. Must work for empty lists, and for odd/even-length lists.
• Deliverables:
  1. The function implementation.
  2. Brief correctness reasoning.
  3. Time and space complexity.
  4. Tests that demonstrate in-place behavior (e.g., object id unchanged) and cover edge cases like [], [1], and [1, 4, 8, 12, 16, 20] → [20, 16, 12, 8, 4, 1].