culsans
Thread-safe async-aware queue for Python
Decision gist · record as of 2026-08-14
Yes, if you need to bridge sync and async code in the same process. The low install friction, permissive ISC license, active maintenance, and broad concurrency framework support make it a solid choice for this specific problem. The Alpha status is not a blocker given recent activity and zero known vulnerabilities, but test it in your target concurrency mix before production use.AI-flagged interpretation of the facts on this page — verify before relying
Before you install
- Requires Python 3.8 or later; async usage requires asyncio, trio, or curio; sync usage with eventlet or gevent requires those libraries installed separately.
- Low install friction with only 2 runtime dependencies (aiologic and typing-extensions).
- Actively maintained with recent commits; marked as Alpha but in active development since 2024-11-02.
License · maintenance · safety
permissive license (permissive) — ISC License (permissive) places minimal restrictions on use, modification, and distribution; suitable for both open-source and proprietary projects.
last release 2025-12-31 (226 days) · last repo commit 2026-08-10 · 62 stars
0 known vulnerabilities (OSV.dev, 2026-08-14) · 2,892,340 downloads/mo, #2,838 on PyPI
Alternatives
Verify before relying
import culsans
queue = culsans.Queue()
# Sync side: queue.sync_q.put(item)
# Async side: await queue.async_q.get()
queue.shutdown()- Whether the checkpoint behavior inherited from aiologic has measurable performance impact in typical workloads.
- Real-world stability and maturity signals beyond the Alpha classification and download metrics.
What it is and what it does
Culsans is a dual-interface queue library that lets synchronous and asynchronous code communicate through a single queue object. It exposes a `.sync_q` property for threaded, eventlet, or gevent code and an `.async_q` property for asyncio, trio, or curio code, allowing you to bridge concurrency models that normally don't mix. The synchronous interface is fully compatible with Python's standard queue module, while the asynchronous interface follows asyncio queue semantics.
The library is built on aiologic and inspired by janus, but extends support to include trio and curio on the async side, and eventlet and gevent on the sync side. It includes features like dynamic maxsize adjustment, peek operations, atomic clearing, and the ability to subclass queues with custom storage backends. All internal methods are called in exclusive access mode, so custom subclasses don't need to worry about thread-safety.
Use it for
- Bridging legacy synchronous code running in threads with new asyncio-based services in the same application.
- Distributing work between a thread pool and an async task group without manual synchronization primitives.
- Building adapter layers that accept messages from both sync and async producers and route them appropriately.
- Migrating from standard queue to async-aware queues while keeping existing threaded code intact.
- Coordinating between eventlet or gevent greenlets and trio or asyncio tasks in polyglot concurrency setups.
Worth the install?
AI-flagged interpretation of the facts on this page. Verify before relying on it.
Yes, if you need to bridge sync and async code in the same process.
The low install friction, permissive ISC license, active maintenance, and broad concurrency framework support make it a solid choice for this specific problem. The Alpha status is not a blocker given recent activity and zero known vulnerabilities, but test it in your target concurrency mix before production use.
Install
culsans on PyPI
Before you install
Low install friction with only 2 runtime dependencies (aiologic and typing-extensions). Actively maintained with recent commits; marked as Alpha but in active development since 2024-11-02.
Requires Python 3.8 or later; async usage requires asyncio, trio, or curio; sync usage with eventlet or gevent requires those libraries installed separately.
License in practice
ISC License (permissive) places minimal restrictions on use, modification, and distribution; suitable for both open-source and proprietary projects.
Quickstart
import culsans
queue = culsans.Queue()
# Sync side: queue.sync_q.put(item)
# Async side: await queue.async_q.get()
queue.shutdown()Verify before relying
- Whether the checkpoint behavior inherited from aiologic has measurable performance impact in typical workloads.
- Real-world stability and maturity signals beyond the Alpha classification and download metrics.
Package facts
| License | permissive license permissive |
| Python support | Supports the current Python release >=3.8 |
| Install friction | Low. Pure-Python wheel |
| Runtime dependencies | 2 packagesaiologictyping-extensions |
| Maintenance | Actively maintained 226 days since the last release |
| Last repo commit | |
| First released | |
| Downloads | 2,892,340 / month, #2,838 on PyPI 30-day window, as of 2026-08-14 |
| Known vulnerabilities | None known OSV.dev, checked 2026-08-14 |
| Classifiers | Development Status :: 3 - AlphaFramework :: AnyIOFramework :: AsyncIOFramework :: TrioIntended Audience :: DevelopersLicense :: OSI Approved :: ISC License (ISCL)Operating System :: OS IndependentProgramming Language :: Python :: 3 :: OnlyProgramming Language :: Python :: 3.10Programming Language :: Python :: 3.11Programming Language :: Python :: 3.12Programming Language :: Python :: 3.13Programming Language :: Python :: 3.14Programming Language :: Python :: 3.8Programming Language :: Python :: 3.9Programming Language :: Python :: Free Threading :: 2 - BetaProgramming Language :: Python :: Implementation :: CPythonProgramming Language :: Python :: Implementation :: PyPyTopic :: Software Development :: Libraries :: Python ModulesTyping :: Typed |
Evidence: culsans-0.11.0-py3-none-any.whl
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See also janus · aiologic · aiochannel · anyio · gcloud-rest-taskqueue · greenback · gcloud-aio-taskqueue · synchronicity · duet · psycogreen