""" ActiveState: http://code.activestate.com/recipes/578634-pyqt-pyside-thread-safe-callbacks-main-loop-integr/ ref and proxy classes are based on: http://code.activestate.com/recipes/81253/#c5 Modified proxy to support a quiet concept for callbacks that can simply pass if they were not valid, instead of raising an exception. Callback event dispatch based on: http://code.activestate.com/recipes/578299-pyqt-pyside-thread-safe-global-queue-main-loop-int/ Modified to simplify the process, by removing the Queue and threaded dispatcher, and just using a more developed Event object that posts directly to the event loop. """ import weakref import types from functools import partial from multiprocessing.pool import ThreadPool __all__ = [ "ref", "proxy", "CallbackEvent", "CallbackThreadPool", ] class ref(object): """ A weak method implementation """ def __init__(self, method): try: if method.im_self is not None: # bound method self._obj = weakref.ref(method.im_self) else: # unbound method self._obj = None self._func = method.im_func self._class = method.im_class except AttributeError: # not a method self._obj = None self._func = method self._class = None def __call__(self): """ Return a new bound-method like the original, or the original function if refers just to a function or unbound method. Returns None if the original object doesn't exist """ if self.is_dead(): return None if self._obj is not None: # we have an instance: return a bound method return types.MethodType(self._func, self._obj(), self._class) else: # we don't have an instance: return just the function return self._func def is_dead(self): """ Returns True if the referenced callable was a bound method and the instance no longer exists. Otherwise, return False. """ return self._obj is not None and self._obj() is None def __eq__(self, other): try: return type(self) is type(other) and self() == other() except: return False def __ne__(self, other): return not self == other # # The modified proxy class, adding a quiet option # class proxy(ref): """ Exactly like ref, but calling it will cause the referent method to be called with the same arguments. If the referent's object no longer lives, ReferenceError is raised. If quiet is True, then a ReferenceError is not raise and the callback silently fails if it is no longer valid. """ def __init__(self, method, quiet=False): super(proxy, self).__init__(method) self._quiet = quiet def __call__(self, *args, **kwargs): func = ref.__call__(self) if func is None: if self._quiet: return else: raise ReferenceError('object is dead') else: return func(*args, **kwargs) def __eq__(self, other): try: func1 = ref.__call__(self) func2 = ref.__call__(other) return type(self) == type(other) and func1 == func2 except: return False # # PyQt4 / PySide Thread-Safe Callback Dispatch # try: from PySide import QtGui, QtCore except ImportError: from PyQt4 import QtGui, QtCore class _Invoker(QtCore.QObject): def customEvent(self, e): e.callback() class CallbackEvent(QtCore.QEvent): """ A custom QEvent that contains a callback reference Also provides class methods for conveniently executing arbitrary callback, to be dispatched to the event loop. """ EVENT_TYPE = QtCore.QEvent.Type(QtCore.QEvent.registerEventType()) __invoker = _Invoker() def __init__(self, func, *args, **kwargs): super(CallbackEvent, self).__init__(self.EVENT_TYPE) self.func = func self.args = args self.kwargs = kwargs def callback(self): """ Convenience method to run the callable. Equivalent to: self.func(*self.args, **self.kwargs) """ self.func(*self.args, **self.kwargs) @classmethod def post(cls, func, *args, **kwargs): """ Post a callable to run in the main thread """ cls.post_to(cls.__invoker, func, *args, **kwargs) @classmethod def post_to(cls, receiver, func, *args, **kwargs): """ Post a callable to be delivered to a specific receiver as a CallbackEvent. It is the responsibility of this receiver to handle the event and choose to call the callback. """ # We can create a weak proxy reference to the # callback so that if the object associated with # a bound method is deleted, it won't call a dead method if not isinstance(func, proxy): reference = proxy(func, quiet=True) else: reference = func event = cls(reference, *args, **kwargs) # post the event to the given receiver QtGui.QApplication.postEvent(receiver, event) class CallbackThreadPool(ThreadPool): """ Simple wrapper around ThreadPool to wrap callbacks in a weakref that get posted as CallbackEvents in the main thread. """ def apply_async(self, fn, args=None, kwargs=None, callback=None): proxyCbk = self._async_helper(callback) args = args or tuple kwargs = kwargs or {} return super(CallbackThreadPool, self).apply_async(fn, args, kwargs, proxyCbk) def map_async(self, fn, iterable, chunk=None, callback=None): proxyCbk = self._async_helper(callback) return super(CallbackThreadPool, self).map_async(fn, iterable, chunk, callback) @staticmethod def _async_helper(callback): if callback: proxyCbk = partial(CallbackEvent.post, proxy(callback, quiet=True)) else: proxyCbk = None return proxyCbk if __name__ == "__main__": # # Usage Example # import time from threading import Event class Gui(QtGui.QDialog): def __init__(self): super(Gui, self).__init__() self.resize(250, 300) self._list = QtGui.QListWidget(self) self._button1 = QtGui.QPushButton("Test CallbackEvent", self) self._button2 = QtGui.QPushButton("Test CallbackPool", self) layout = QtGui.QVBoxLayout(self) layout.setSpacing(2) layout.addWidget(self._button1) line = QtGui.QFrame(self) line.setFrameStyle(line.HLine) layout.addSpacing(6) layout.addWidget(line) layout.addSpacing(6) layout.addWidget(self._list) layout.addWidget(self._button2) self._pool = CallbackThreadPool(4) self._button1.clicked.connect(self.runCallbackEvents) self._button2.clicked.connect(self.runCallbackPool) def customEvent(self, event): print "Running callback from Gui.customEvent()" event.callback() def runCallbackEvents(self): self._list.clear() self._list.addItem("Printing results to console...") thread = Worker(self) thread.start() def runCallbackPool(self): self._list.clear() def action(a, b): time.sleep(1) return a+b def callback(result): self._list.addItem("Result: %s" % result) for i in xrange(20): self._pool.apply_async(action, (i, i), callback=callback) # Just some random worker class Worker(QtCore.QThread): def __init__(self, parent=None): super(Worker, self).__init__(parent) self.__quitting = Event() def run(self): for i in xrange(5): msg = "#{0}: Hi".format(i) # Instruct the say() method to run in the main thread, # being delivered to the parent CallbackEvent.post_to(self.parent(), self.say, msg) self.msleep(200) # Run the same callback, but without a specific receiver. # This will just be run directly in an anonymous receiver. CallbackEvent.post(self.say, msg) self.msleep(200) # And lets just have one happen from this worker thread too self.say(msg) self.msleep(200) if self.__quitting.is_set(): break print "All done!" def stop(self): self.__quitting.set() self.wait() def say(self, word): mainThread = QtGui.qApp.thread() isMainThread = mainThread == self.currentThread() print word, "from", "main" if isMainThread else "worker", "thread" app = QtGui.QApplication([]) gui = Gui() gui.show() gui.raise_() app.exec_()