I'm attempting to run a CPU intensive task in a separate QThread using PyQt5. I've tried several permutations of the code, only to get one of 2 unwanted results.
Either this error: "QThread: Destroyed while thread is still running"
Or the GUI hangs as if the separate thread doesn't exist!
I've created a basic example. How do I get it to work like I expect?
Most importantly, I want to run the QThread based on whether a condition is True or not. If it's True, show a warning that lets the user cancel the operation. If False, just run the thread.
Here's the code:
from PyQt5.QtWidgets import QApplication, QWidget, QMainWindow, QPushButton, QVBoxLayout, QHBoxLayout, QMessageBox
from PyQt5.QtCore import QThread, QObject
class createMainWindow(QMainWindow):
def __init__(self):
super().__init__()
self.setFixedSize(300, 100)
self.setWindowTitle('Thread testing')
self.show()
class createMainWidget(QWidget):
def __init__(self):
super().__init__()
threadButton = QPushButton('Start thread!')
threadButton.clicked.connect(self.startThread)
layout = QVBoxLayout(self)
layout.addWidget(threadButton)
def startThread(self):
thread = QThread()
worker = createWorker()
worker.moveToThread(thread)
thread.started.connect(worker.run) # It's like this is invisible. It should work.
# I want to display a warning message if a certain condition is met. If the warning is displayed, the user has the option of not continuing.
displayMessage = True
if displayMessage == True:
warningMessage = QMessageBox()
warningMessage.setIcon(QMessageBox.Warning)
warningMessage.setWindowTitle('Warning')
warningMessage.setText('Be warned!')
warningMessage.setStandardButtons(QMessageBox.Ok | QMessageBox.Cancel)
warningMessage.accepted.connect(thread.start) # Why does this destroy the QThread straight away???
warningMessage.exec_()
# The condition is false, therefore just start the thread.
elif displayMessage == False:
thread.start() # This destroys the QThread as well. Why?
class createWorker(QObject):
def __init__(self):
super().__init__()
def run(self):
print('Secondary thread working')
i = 0
while i < 1000000000: i += 1 # Simulate CPU intensive activity
print('Done')
app = QApplication([])
mainWidget = createMainWidget()
mainWindow = createMainWindow()
mainWindow.setCentralWidget(mainWidget)
app.exec_()
