multithreading - What's the correct pattern for threading in a python qt5 application? -


i'm trying write pyqt5 application long running, not cpu intensive process. i'd able run without hanging ui, i'm trying use threading, since doesn't seem can run thread , have stop after gone through code can run again, i've tried setting thread wait variable change before running.

i know can't correct pattern running long processes in pyqt app. 

import time import threading pyqt5 import qtwidgets, uic   class myapp(qtwidgets.qmainwindow):     _run_thread = false      def __init__(self):         qtwidgets.qmainwindow.__init__(self)         self.ui = uic.loadui('myapp.ui', self)          self.ui.start_thread_button.clicked.connect(self._run_thread_function)          self._thread = threading.thread(target=self._run_thread_callback)         self._thread.daemon = true         self._thread.start()          self.ui.show()      def _run_thread_callback(self):         while true:             if self._run_thread:                 print("running thread code...")                 time.sleep(10)                 print("thread code finished")                 self._run_thread = false      def _run_thread_function(self):         print("starting thread...")         self._run_thread = true   def main():     app = qtwidgets.qapplication(sys.argv)     myapp()     sys.exit(app.exec_())  if __name__ == '__main__':     main()

below simple demo showing how start , stop worker thread, , safely comminucate gui thread.

import sys pyqt5 import qtcore, qtwidgets  class worker(qtcore.qthread):     datasent = qtcore.pyqtsignal(dict)      def __init__(self, parent=none):         super(worker, self).__init__(parent)         self._stopped = true         self._mutex = qtcore.qmutex()      def stop(self):         self._mutex.lock()         self._stopped = true         self._mutex.unlock()      def run(self):         self._stopped = false         count in range(10):             if self._stopped:                 break             self.sleep(1)             data = {                 'message':'running %d [%d]' % (                     count, qtcore.qthread.currentthreadid()),                 'time': qtcore.qtime.currenttime(),                 'items': [1, 2, 3],                 }             self.datasent.emit(data)  class window(qtwidgets.qwidget):     def __init__(self):         super(window, self).__init__()         self.edit = qtwidgets.qplaintextedit()         self.edit.setreadonly(true)         self.button = qtwidgets.qpushbutton('start')         self.button.clicked.connect(self.handlebutton)         layout = qtwidgets.qvboxlayout(self)         layout.addwidget(self.edit)         layout.addwidget(self.button)         self._worker = worker()         self._worker.started.connect(self.handlethreadstarted)         self._worker.finished.connect(self.handlethreadfinished)         self._worker.datasent.connect(self.handledatasent)      def handlethreadstarted(self):         self.edit.clear()         self.button.settext('stop')         self.edit.appendplaintext('started')      def handlethreadfinished(self):         self.button.settext('start')         self.edit.appendplaintext('stopped')      def handledatasent(self, data):         self.edit.appendplaintext('message [%d]' %             qtcore.qthread.currentthreadid())         self.edit.appendplaintext(data['message'])         self.edit.appendplaintext(data['time'].tostring())         self.edit.appendplaintext(repr(data['items']))      def handlebutton(self):         if self._worker.isrunning():             self._worker.stop()         else:             self._worker.start()  if __name__ == '__main__':      app = qtwidgets.qapplication(sys.argv)     window = window()     window.setgeometry(500, 100, 400, 400)     window.show()     sys.exit(app.exec_())

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