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Implementation of the PEP 3156 Event-Loop with Qt.

Project description

Implementation of the PEP 3156 Event-Loop with Qt


Mark Harviston <>, Arve Knudsen <>

Latest Version Downloads Supported Python versions License Development Status Linux (Travis CI) Build Status Windows (Appveyor) Build Status Gitter


Quamash requires Python 3.4 or Python 3.3 with the backported asyncio library and either PyQt4, PyQt5 or PySide.


pip install quamash

Upgrade from Version 0.4 to 0.5

The loop context manager will no longer set the event loop only close it.

Instead of:

with loop:


# ...
with loop:

It is recommended that you call asyncio.set_event_loop as early as possible (immediately after instantiating the loop), to avoid running asynchronous code before asyncio.set_event_loop is called.

If you’re using multiple different loops in the same application, you know what you’re doing (or at least you hope you do), then you can ignore this advice.


import sys
import asyncio
import time

from PyQt5.QtWidgets import QApplication, QProgressBar
from quamash import QEventLoop, QThreadExecutor

app = QApplication(sys.argv)
loop = QEventLoop(app)
asyncio.set_event_loop(loop)  # NEW must set the event loop

progress = QProgressBar()
progress.setRange(0, 99)

async def master():
    await first_50()
    with QThreadExecutor(1) as exec:
        await loop.run_in_executor(exec, last_50)
    # TODO announce completion?

async def first_50():
    for i in range(50):
        await asyncio.sleep(.1)

def last_50():
    for i in range(50,100):
        loop.call_soon_threadsafe(progress.setValue, i)

with loop: ## context manager calls .close() when loop completes, and releases all resources


Version 0.6.1 * Python 3.7 support (no automated test coverage)

Version 0.6.0

  • Lots of bugfixes and performance improvements.

Version 0.5.5

  • Fix #62 a serious memory leak by switching from QTimer to QObject.timerEvent.

Version 0.5.4

  • Remove unnecessary QObjects

  • Officially add Python 3.5 support (CI configuration and change)

  • Fix #55

  • Better compatibility with behavior of default event loop (#59)

  • Remove _easycallback and replace with _makeSignaller

Version 0.5.3

Version 0.5.2

  • Fixes to tests, and CI configuration

  • Fixes #35 and #31 (both minor bugs)

  • Uploade wheels to PyPI

Version 0.5.1

  • Fixes rst syntax error in this README

Version 0.5

  • Deprecation of event loop as means to asyncio.set_event_loop, now must be called explicitly.

  • Possible fix to notifiers being called out-of-order (see #25, #27, and e64119e)

  • Better loop cleanup

  • CI Tests pass on windows now

  • Testing improvements

  • Python 3.3 Support. (probably always supported, but it’s offially supported/tested now)

Version 0.4.1

  • Improvements to PEP-3156 Conformance

  • Minor Test Improvements

Version 0.4

  • Major improvements to tests

    • integration with Travis CI

    • more tests

    • all tests pass

    • cross platform/configuration tests

  • Bug #13 discovered and fixed

  • Force which Qt Implementation to use with QUQMASH_QTIMPL environment variable.

  • Implement QEventLoop.remove_reader and QEventLoop.remove_writer

  • PyQt4 Support

  • PyQt5 Support

  • Support multiprocessing executors (ProcessPoolExecutor))

  • Improvements to code quality

Version 0.3

First version worth using.


Quamash is tested with pytest; in order to run the test suite, just install pytest and execute py.test on the commandline. The tests themselves are beneath the ‘tests’ directory.

Testing can also be done with tox. The current tox setup in tox.ini requires PyQT4/5 and PySide to be installed globally. (pip can’t install PyQt into a virtualenv which is what tox will try to do). For this reason it may be good to run tox tests while specificying which environments to run. e.g. tox -e py34-pyqt5 to test python 3.4 with PyQt5. It is unlikely this tox configuration will work well on Windows especially since PyQt5 and PyQt4 cannot coexist in the same python installation on Windows. Also the PyQt4 w/ Qt5 oddity appears to be mostly a windows only thing too.

Style testing is also handled by tox. Run tox -e flake8.

Code Coverage

Getting a full coverage support is quite time consuming. In theory this could by done with pytest-xdist, but I haven’t had time to make that work. Install pytest-cov with pip install pytest-cov then run py.test --cov quamash then append a dot and an identifier the generated .coverage file. For example, mv .coverage .coverage.nix.p33.pyside then repeat on all the platforms you want to run on. (at least linux and windows). Put all the .coverage.* files in one directory that also has quamash source code in it. cd to that directory and run coverage combine finally run coverage html for html based reports or coverage report for a simple report. These last commands may fail with errors about not being able to find source code. Use the .coveragerc file to specify equivelant paths. The default configuration has linux source code in /quamash and windows source at C:\quamash.

Continuous Integration & Supported Platforms

This project uses Travis CI to perform tests on linux (Ubuntu 12.04 LTS “Precise Pangolin”) and Appveyor (Windows Server 2012 R2, similar to Windows 8) to perform continuous integration.

On linux, Python 3.3 and 3.4 with PySide, PyQt4, and PyQt5 are tested. On windows, Python 3.4 with PySide, PyQt4 and PyQt5 are tested, but Python 3.3 is only tested with PySide since binary installers for PyQt are not provided for Python 3.3 (at least not the newest versions of PyQt), and compiling from source probably isn’t worth it.

Python 3.5 is now tested on linux with PyQt4 and PyQt5.

Testing Matrix



PySide (Qt4)

PySide 2 (Qt5)

Linux - Python 3.3





Linux - Python 3.4





Linux - Python 3.5





Windows - Python 3.3





Windows - Python 3.4





Windows - Python 3.5






You may use, modify, and redistribute this software under the terms of the BSD License. See LICENSE.


Tulip related projects are being named after other flowers, Quamash is one of the few flowers that starts with a “Q”.

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