qasync
Python library for using asyncio in Qt-based applications
Decision gist · record as of 2026-08-14
Yes. qasync is actively maintained, has no external dependencies, carries a permissive license, and solves a real pain point—integrating asyncio into Qt apps cleanly. The codebase is stable (Production/Stable classifier), tested across major platforms, and has seen regular updates. Install it if you're building a PyQt/PySide application and want to use async/await instead of threading.AI-flagged interpretation of the facts on this page — verify before relying
Before you install
- Requires PyQt5, PyQt6, PySide2, or PySide6 to be installed separately; Python >=3.8 required.
- Low friction: pure Python wheel with no runtime dependencies.
- Actively maintained as of July 2026 with 405 repository stars and a clear maintenance commitment stated in the project.
License · maintenance · safety
BSD-2-Clause (permissive) — BSD-2-Clause permissive license allows use, modification, and redistribution with minimal restrictions—suitable for both open and closed projects.
last release 2025-08-28 (351 days) · last repo commit 2026-07-06 · 405 stars
0 known vulnerabilities (OSV.dev, 2026-08-14) · 370,908 downloads/mo, #7,173 on PyPI
Alternatives
Verify before relying
pip install qasync
from qasync import QApplication, QEventLoop
import asyncio
app = QApplication(sys.argv)
loop = QEventLoop(app)
asyncio.set_event_loop(loop)
# Use async functions in Qt slots and event handlers- Whether the package works with all four Qt bindings (PyQt5/6, PySide2/6) equally well or has known limitations with any.
- Performance characteristics when running CPU-intensive tasks via QThreadExecutor compared to standard threading approaches.
- Compatibility with recent Python 3.13+ versions given the stated support ceiling of <3.14.
What it is and what it does
qasync bridges asyncio and Qt by implementing a PEP 3156 event loop that runs inside a Qt application's main thread. This lets you write async/await code directly in PyQt/PySide event handlers and slots, replacing the need for manual threading with cleaner, more readable coroutine-based logic.
The package provides decorators like @asyncSlot and @asyncClose to mark async event handlers, and exposes run_in_executor for CPU-bound work on thread pools. It has no runtime dependencies beyond a Qt binding (PyQt5/6 or PySide2/6) and maintains active development with support for Python 3.8 and later.
Use it for
- Build responsive Qt GUIs that fetch data from APIs without blocking the UI thread using async/await.
- Replace QThread boilerplate with cleaner asyncio patterns for background tasks in PyQt/PySide apps.
- Coordinate multiple concurrent operations (timers, I/O, network calls) within a single Qt event loop.
- Offload CPU-intensive work to thread pools via run_in_executor while keeping the UI responsive.
- Migrate existing asyncio codebases to Qt-based desktop applications without rewriting async logic.
Worth the install?
AI-flagged interpretation of the facts on this page. Verify before relying on it.
Yes.
qasync is actively maintained, has no external dependencies, carries a permissive license, and solves a real pain point—integrating asyncio into Qt apps cleanly. The codebase is stable (Production/Stable classifier), tested across major platforms, and has seen regular updates. Install it if you're building a PyQt/PySide application and want to use async/await instead of threading.
Install
qasync on PyPI
Before you install
Low friction: pure Python wheel with no runtime dependencies. Actively maintained as of July 2026 with 405 repository stars and a clear maintenance commitment stated in the project.
Requires PyQt5, PyQt6, PySide2, or PySide6 to be installed separately; Python >=3.8 required.
License in practice
BSD-2-Clause permissive license allows use, modification, and redistribution with minimal restrictions—suitable for both open and closed projects.
Quickstart
pip install qasync
from qasync import QApplication, QEventLoop
import asyncio
app = QApplication(sys.argv)
loop = QEventLoop(app)
asyncio.set_event_loop(loop)
# Use async functions in Qt slots and event handlersVerify before relying
- Whether the package works with all four Qt bindings (PyQt5/6, PySide2/6) equally well or has known limitations with any.
- Performance characteristics when running CPU-intensive tasks via QThreadExecutor compared to standard threading approaches.
- Compatibility with recent Python 3.13+ versions given the stated support ceiling of <3.14.
Package facts
| License | BSD-2-Clause permissive |
| Python support | Supports the current Python release >=3.8 |
| Install friction | Low. Pure-Python wheel |
| Runtime dependencies | None |
| Maintenance | Actively maintained 351 days since the last release |
| Last repo commit | |
| First released | |
| Downloads | 370,908 / month, #7,173 on PyPI 30-day window, as of 2026-08-14 |
| Known vulnerabilities | None known OSV.dev, checked 2026-08-14 |
| Classifiers | Development Status :: 5 - Production/StableEnvironment :: X11 Applications :: QtIntended Audience :: DevelopersOperating System :: MacOSOperating System :: MacOS :: MacOS XOperating System :: MicrosoftOperating System :: Microsoft :: WindowsOperating System :: POSIXOperating System :: POSIX :: LinuxTopic :: Software Development :: Libraries :: Python Modules |
Evidence: qasync-0.28.0-py3-none-any.whl
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See also nest-asyncio · QtPy · qtmonaco · PySide6 · superqt · nest-asyncio2 · aioprocessing · asyncio · syncer · asyncio-atexit