Python queues with deque
A queue removes the oldest item first. deque supports efficient additions and removals at either end; append plus popleft implements a FIFO queue.
Python
from collections import deque
queue = deque(["A", "B"])
queue.append("C")
print(queue.popleft())
print(queue.popleft())
print(list(queue))
assert queue.popleft() == "C"
assert not queue