aiodeque

A drop-in collections.deque replacement with async methods for producer/consumer coordination.

Why aiodeque?

asyncio.Queue only does FIFO. aiodeque gives you a double-ended queue with async waiting on both ends:

• Pop from right or left, append to right or left
• Waiters block when the deque is empty (pop) or full (append with maxlen)
• Fully compatible with collections.deque — all sync methods work as-is

Requirements

• Python >= 3.11
• No runtime dependencies

Installation

pip install aiodeque

uv add aiodeque

Quick Start

import asyncio
from aiodeque import deque

async def main():
    d: deque[int] = deque(maxlen=5)

    async def producer():
        for i in range(10):
            await d.aappend(i)

    async def consumer():
        for _ in range(10):
            item = await d.apopleft()
            print(item)

    await asyncio.gather(producer(), consumer())

asyncio.run(main())

Async API

Method	Blocks when…
await d.apop()	deque is empty
await d.apopleft()	deque is empty
await d.aappend(item)	deque is full (maxlen set)
await d.aappendleft(item)	deque is full (maxlen set)
await d.aextend(iterable)	deque is full for each item
await d.aextendleft(iterable)	deque is full for each item
await d.ainsert(i, item)	deque is full (maxlen set)

All other collections.deque methods (.append(), .pop(), .rotate(), etc.) are inherited and work unchanged.

Evicting mode

Pass evict=True to aappend, aappendleft, aextend, or aextendleft to drop the oldest element instead of waiting when the deque is full:

d: deque[int] = deque([1, 2, 3], maxlen=3)
evicted = await d.aappend(4, evict=True)   # evicted == 1, d == [2, 3, 4]
evicted = await d.aappendleft(0, evict=True)  # evicted == 4, d == [0, 2, 3]

• aappend(..., evict=True) evicts from the left (oldest-first FIFO).
• aappendleft(..., evict=True) evicts from the right.
• Returns the evicted element, or None if the deque was not full.
• When the deque is not full, behaves identically to the non-evicting call.

Behavior Notes

• Sync mutations do not wake async waiters — if you call d.append() directly, tasks waiting in apopleft() will not be notified. Use async methods when coordinating between producers and consumers.
• Cancellation safe — cancelling an await removes the waiter cleanly; no item is lost and the next waiter is woken up if appropriate.
• FIFO waiter ordering — waiters are served in the order they started waiting.
• Lazy initialization — internal waiter queues are only allocated on first async use; sync-only usage has no overhead.

vs asyncio.Queue

Feature	asyncio.Queue	aiodeque
FIFO get/put	Yes	Yes (apopleft / aappend)
Pop from right	No	Yes (apop)
Append to left	No	Yes (aappendleft)
Insert at index	No	Yes (ainsert)
Rotate / slice	No	Yes (inherited from deque)
maxsize / maxlen	Yes	Yes
Evicting append	No	Yes (evict=True)
task_done / join	Yes	No
Sync access	No	Yes (all collections.deque methods)
Type-parameterized	No	Yes (deque[T])

Contributing

See CONTRIBUTING.md for development setup and contribution guidelines.

License

MIT