Pause and resume QThread

Question

I am trying to pause QThread and resume it.

So, I have an RFID reader loop in QThread, and I want to pause an infinite loop when the reader receives an RFID code. After that, a db check occurs. At the end of the check, I want to resume RFID reading to get other codes.

MVCE:

def main():
    global Thread
    app = QtGui.QApplication(sys.argv)
    main = Main()
    Thread = RFID_Thread()
    Thread.rfid_event.connect(Main().on_event)
    Thread.start()
    sys.exit(app.exec_())

class Main(object):
    def __init__(self):
        self.accueil = MainWindow(self)
        self.access = AccessWindow()
        self.accueil.show()

    def on_event(self, data):
        # I WANT TO PAUSE THE QTHREAD HERE

        ###################################
        #   CHECKING DB & SHOWING UI      #
        ###################################

        # AND RESUME IT HERE
class RFID_Thread(QtCore.QThread):
    rfid_event = pyqtSignal(str, name='rfid_event')
    def run(self):
        while 1:
            ser = serial.Serial(port=Serial_Port, baudrate=Serial_Baudrate)
            a = ser.read(19).encode('hex')
            ser.close()
            if len(a) <> 0:
                Code = a[14:]
                self.rfid_event.emit(Code)
                time.sleep(2)

if __name__=='__main__':
    main()

the code cannot be reproduced because you need an RFID reader, but we can simulate it with these two lines instead of opening the serial port and reading the data from it:

a = "**************e20030654408021520403f4b"
time.sleep(4)

I tried to use the status variable, but it does not work.

Answer 1

Finally, I solved the problem myself.

MVCE:

def main():
    global Thread
    app = QtGui.QApplication(sys.argv)
    main = Main()
    Thread = RFID_Thread()
    Thread.rfid_event.connect(Main().on_event)
    Thread.start()
    sys.exit(app.exec_())

class Main(object):
    def __init__(self):
        self.accueil = MainWindow(self)
        self.access = AccessWindow()
        self.accueil.show()

    def on_event(self, data):
        # I WANT TO PAUSE THE QTHREAD HERE

        Thread.Pause = False
        ###################################
        #   CHECKING DB & SHOWING UI      #
        ###################################

        # AND RESUME IT HERE
        Thread.Pause = True
class RFID_Thread(QtCore.QThread):
    rfid_event = pyqtSignal(str, name='rfid_event')
    Pause = True
    def run(self):
        while 1:
            if Pause:
                  ser = serial.Serial(port=Serial_Port, baudrate=Serial_Baudrate)
                  a = ser.read(19).encode('hex')
                  ser.close()
                  if len(a) <> 0:
                         Code = a[14:]
                         self.rfid_event.emit(Code)
                         time.sleep(2)
            else:
                  continue
 if __name__=='__main__':
    main()

Finally, the State variable was the solution!

Answer 2

, , , .

import sys,time
from PyQt5 import QtWidgets,QtCore

class Thread(QtCore.QThread):
    def __init__(self):
        QtCore.QThread.__init__(self)
        self.pause = False
    def run(self):
        for i in range(100):
            if self.pause:
                print("Paused")
                while self.pause:time.sleep(1)
            print("Number: "+str(i))
            time.sleep(1)
class App(QtWidgets.QWidget):
    def __init__(self):
        super().__init__()
        self.title = 'QThread Pause test'
        self.left = 10
        self.top = 10
        self.width = 320
        self.height = 200
        self.initUI()
    def initUI(self):
        self.setWindowTitle(self.title)
        self.setGeometry(self.left, self.top, self.width, self.height)
        self.button = QtWidgets.QPushButton('Pause', self)
        self.button.move(175,75) 
        self.button.clicked.connect(self.thread_pause_resume)
        self.thread = Thread()
        self.show()
        self.thread.start()
    @QtCore.pyqtSlot()
    def thread_pause_resume(self):
        if self.button.text() == "Pause":
            self.thread.pause = True
            self.button.setText("Resume")
        else:
            self.thread.pause = False
            self.button.setText("Pause")

if __name__ == '__main__':
    app = QtWidgets.QApplication(sys.argv)
    ex = App()
    sys.exit(app.exec_())