Test your knowledge: Python Double-Ended Queues

Review

1. Which pair adds an item to the left end and removes an item from the left end, respectively?

   appendleft() inserts on the left and popleft() removes and returns the leftmost item.
2. A queue receives items with append(). Which method serves the oldest item first?

   append() adds to the right; popleft() removes from the left, preserving first-in, first-out order.
3. Why is deque usually preferred to repeatedly calling list.pop(0) for a large waiting line?

   A list generally shifts the remaining elements after removing its first item. deque is designed for efficient additions and removals at either end.
4. A full deque has maxlen=2 and contains ["a", "b"]. What happens after append("c")?

   When a bounded deque is full, appending on the right discards an item from the left.
5. What does deque.rotate(-1) do?

   A negative rotation shifts the deque to the left; the item formerly at the leftmost end moves to the right end.