- FIFO - first in first out - works like normal list - queue problems are generally more difficult & less common than stacks - most common use is to implement [[BFS]], rare usage otherwise ``` # Declaration: we will use deque from the collections module import collections queue = collections.deque() # If you want to initialize it with some initial values: queue = collections.deque([1, 2, 3]) # Enqueueing/adding elements: queue.append(4) queue.append(5) # Dequeuing/removing elements: queue.popleft() # 1 queue.popleft() # 2 # Check element at front of queue (next element to be removed) queue[0] # 3 # Get size len(queue) # 3 ```