Simple example of threaded loop

thread2.py

from PyQt5.QtCore import *
from PyQt5.QtWidgets import *
from itertools import count, islice
from time import sleep

class Threaded(QObject):
    count=pyqtSignal(int)

    def __init__(self, parent=None, **kwargs):
        super().__init__(parent, **kwargs)

        self._count=0
        self._looping=False

    @pyqtSlot()
    def start(self): print("Thread started")

    @pyqtSlot()
    def loop(self):
        self._count=0
        self._looping=True
        while self._looping:
            self._count+=1
            self.count.emit(self._count)
            qApp.processEvents()
            sleep(1.)

    @pyqtSlot()
    def stopLoop(self):
        self._looping=False

class GUI(QWidget):
    startLoop=pyqtSignal()
    stopLoop=pyqtSignal()

    def __init__(self, parent=None, **kwargs):
        super().__init__(parent, **kwargs)

        self._thread=QThread()
        self._threaded=Threaded(count=self.displayCount)
        self._thread.started.connect(self._threaded.start)
        self.startLoop.connect(self._threaded.loop)
        self.stopLoop.connect(self._threaded.stopLoop)
        self._threaded.moveToThread(self._thread)
        qApp.aboutToQuit.connect(self._thread.quit)
        self._thread.start()

        l=QVBoxLayout(self)
        l.addWidget(QPushButton("Start", self, clicked=self.startLoop))
        l.addWidget(QPushButton("Stop", self, clicked=self.stopLoop))
        self._countLbl=QLabel("Count:", self)
        l.addWidget(self._countLbl)
        
    @pyqtSlot(int)
    def displayCount(self, count):
        self._countLbl.setText("Count: {}".format(count))

if __name__=="__main__":
    from sys import exit, argv

    a=QApplication(argv)
    g=GUI()
    g.show()
    exit(a.exec_())