Detailed tutorial(Chinese)

https://hgoldfish.com/blogs/article/85/

Integrate eventlet with Qt's eventloop. It is very simple to use:

from hgoldfish.utils import eventlet
app = QApplication()
eventlet.start_application()

After starting the Qt's eventloop, we can make connections as in select-based eventlet applications.

try:
    from eventlet.green.urllib import urlopen
except ImportError:  # for py3k
    from eventlet.green.urllib.request import urlopen

def fetchUrl(url):
    page = urlopen(url).read()
    print(page)

A complete simple example, click Middle Button to download :

import logging; logging.basicConfig(level = logging.DEBUG)
from hgoldfish.utils import eventlet
try:
    from eventlet.green.urllib import urlopen
except ImportError:  # py3k
    from eventlet.green.urllib.request import urlopen

try:
    from PyQt4.QtCore import Qt
    from PyQt4.QtGui import QApplication, QTextBrowser
except ImportError:
    from PyQt5.QtCore import Qt
    from PyQt5.QtGui import QApplication, QTextBrowser


class TestWidget(QTextBrowser):
    def __init__(self):
        QTextBrowser.__init__(self)
        self.operations = eventlet.GreenletGroup()
        self.setPlainText("click middle button to navigate www.163.com")

    def mousePressEvent(self, event):
        if event.button() == Qt.MidButton:
            self.operations.spawn(self.getpage)
            self.operations.spawnWithName("print_number", self.printNumbers)
        QTextBrowser.mousePressEvent(self, event)

    def printNumbers(self):
        i = 0
        while True:
            eventlet.sleep(0.1)
            i += 1
            self.append(str(i))

    def getpage(self):
        page = urlopen("http://www.163.com/").read().decode("gbk", "replace")
        self.setPlainText(page)
        self.operations.kill("print_number")

if __name__ == "__main__":
    app = QApplication([])
    w = TestWidget()
    w.show()
    eventlet.start_application(quitOnLastWindowClosed = True)

Unfortunely, as the greenlet module is broken, we must be very careful to spawn greenlets.

• DO NOT throw any exceptions from greenlet. Or that Python will crash.
• Greenlets SHOULD NOT keep references to its owner. As this situation causes cycled references.If you want to do so, use weakref, or give a try to GreenletGroup, which pass the weak reference of parameters to target function.
• DO NOT start a local Qt eventloop. If you want to do so, use runLocalLoop(). Pay attention to QMessageBox and QDialog.
• Clear exceptions before yield to another greenlet. The Python provide sys.exc_clar() to do so.

This module provide this functions:

• runInNewThread(func, *args, **kwargs) Start a new thread to run func with arguments provided. Block current greenlet, wait for the new thread to finished, and return the value func returned.

• start_application(quitOnLastWindowClosed = True) Start the Qt Application.

• stop_application() Stop the Qt Application. Wait 1 second for greenlets to stop.

• exc_clear() For Python 2.x version, it is sys.exc_clear(). For Python 3.x, it does nothing.

• runLocalLoop(eventloop) & runDialog(dialog) Alias for callMethodInEventLoop(eventloop.exec)

• callMethodInEventLoop(func, *args, **kwargs) Dialogs and local eventloops must run in the greenlet where Qt's main eventloop live in.

The GreenletGroup manages greenlets. It has several methods you may like.

• spawnWithName(name, func, *args, **kwargs) Spawn a new greenlet named name to run the given func with past arguments. All the arguments are past as weakref.proxy.

• spawn(func, *args, **kwargs) Alias for spawnWithName(None, func, *args, **kwargs)

• get(name) Get the greenlet which named name.

• kill(name) Kill the greenlet which named name

• killall() Kill all managed greenlets.