deque
Use fast double-ended queues.
What is a deque?
A deque (pronounced 'deck') is a double-ended queue from the collections module. It supports fast appends and pops from both ends.
Import it with from collections import deque.
from collections import deque
d = deque([1, 2, 3])
print(d)Why not just a list?
Lists are slow when you insert or remove at the front because every element must shift. A deque does front operations in constant time, making it ideal for queues.
from collections import deque
d = deque(['b', 'c'])
d.appendleft('a')
print(d)