PyQt5: Timer in a thread

Question

Problem Description

I'm trying to make an application that collects data, processes it, displays it, and some actuation (open/close valves, etc). As a practice for future applications where I have some stricter time constraints, I want to run the data capture and processing in a separate thread.

My current problem is that it's telling me I cannot start a timer from another thread.

Current code progress

import sys
import PyQt5
from PyQt5.QtWidgets import *
from PyQt5.QtCore import QThread, pyqtSignal

# This is our window from QtCreator
import mainwindow_auto

#thread to capture the process data
class DataCaptureThread(QThread):
    def collectProcessData():
        print ("Collecting Process Data")
    #declaring the timer
    dataCollectionTimer = PyQt5.QtCore.QTimer()
    dataCollectionTimer.timeout.connect(collectProcessData)
    def __init__(self):
        QThread.__init__(self)

    def run(self):
        self.dataCollectionTimer.start(1000);

class MainWindow(QMainWindow, mainwindow_auto.Ui_MainWindow):
    def __init__(self):
        super(self.__class__, self).__init__()
        self.setupUi(self) # gets defined in the UI file
        self.btnStart.clicked.connect(self.pressedStartBtn)
        self.btnStop.clicked.connect(self.pressedStopBtn)

    def pressedStartBtn(self):
        self.lblAction.setText("STARTED")
        self.dataCollectionThread = DataCaptureThread()
        self.dataCollectionThread.start()
    def pressedStopBtn(self):
        self.lblAction.setText("STOPPED")
        self.dataCollectionThread.terminate()


def main():
     # a new app instance
     app = QApplication(sys.argv)
     form = MainWindow()
     form.show()
     sys.exit(app.exec_())

if __name__ == "__main__":
     main()

Any advice on how to get this to work would be appreciated!

Answer 1

You have to move the QTimer to the DataCaptureThread thread, in addition to that when the run method ends, the thread is eliminated so the timer is eliminated, so you must avoid running that function without blocking other tasks. QEventLoop is used for this:

class DataCaptureThread(QThread):
    def collectProcessData(self):
        print ("Collecting Process Data")

    def __init__(self, *args, **kwargs):
        QThread.__init__(self, *args, **kwargs)
        self.dataCollectionTimer = QTimer()
        self.dataCollectionTimer.moveToThread(self)
        self.dataCollectionTimer.timeout.connect(self.collectProcessData)

    def run(self):
        self.dataCollectionTimer.start(1000)
        loop = QEventLoop()
        loop.exec_()