Double-ended queue
= Double-ended queue
= deque
{synonym}
A <double-ended queue> supports insertion and removal at both ends. It combines the access patterns of a <stack> and a <queue> without promising fast arbitrary indexing. For example, appending `a,b` at the right and then `c` at the left produces `c,a,b`; removing at the right returns `b`. A circular <array> or a doubly <linked list> can implement the abstraction, with different allocation and indexing costs. Python's deque provides approximately constant-time end operations, unlike repeatedly inserting at the start of an ordinary list.https://docs.python.org/3/library/collections.html#collections.deque[Python documentation, deque objects]{ref}