CODEWITHSUNDEEP
pythonqthreadpyside2
Saeid Gholizade
Saeid Gholizade

Reputation: 89

PySide2 Qthread crash

I want to use PySide2 Qtcore.Qthread because of Qtcore.Signal, but I end up with this error: Process finished with exit code -1073740791

from PySide2.QtCore import QThread


class Thread(QThread):
    def run(self):
        print('task started')
        k = 0
        for i in range(10000):
            for j in range(5000):
                k += 1
        print('task finished')

Thread().start()

expect to have those prints but I have this error:

Process finished with exit code -1073740791

Update:

so, why this code also throw the same error?

class Thread(QThread):
    done = Signal()

    def __init__(self):
        super(Thread, self).__init__()

    def run(self):
        print('task started')
        k = 0
        for i in range(10000):
            for j in range(5000):
                k += 1
        print('task finished')
        self.done.emit()

class Widget(QtWidgets.QWidget):
    def __init__(self):
        super(Widget, self).__init__()
        btn = QtWidgets.QPushButton('test', parent=self)
        btn.clicked.connect(self.clicked)
        btn.show()

    def clicked(self):
        t = Thread()
        t.done.connect(self.done)
        t.start()

    def done(self):
        print('done')

app = QtWidgets.QApplication()
window = Widget()
window.show()
sys.exit(app.exec_())

Upvotes: 2

Views: 765

Answers (2)

Saeid Gholizade
Saeid Gholizade

Reputation: 89

I found the solution but I don't know why I should do this. the thread should a part of the class.

self.t = Thread()
self.t.done.connect(self.done)
self.t.start()

Upvotes: 0

eyllanesc
eyllanesc

Reputation: 243897

Explanation

If you run your code in a CMD/Terminal you will get the following error:

QThread: Destroyed while thread is still running
Aborted (core dumped)

And the error is caused because the thread is destroyed while it is still running since it is a local variable, on the other hand QThread needs an event loop to run

Solution

import sys
from PySide2.QtCore import QCoreApplication, QThread


class Thread(QThread):
    def run(self):
        print("task started")
        k = 0
        for i in range(10000):
            for j in range(5000):
                k += 1
        print("task finished")


if __name__ == "__main__":
    # create event loop
    app = QCoreApplication(sys.argv)

    th = Thread()
    th.start()

    th.finished.connect(QCoreApplication.quit)
    sys.exit(app.exec_())

Update:

"t" is a local variable that will be eliminated after executing clicked causing the same problem as your initial code, the solution is to prevent it from being destroyed instantly and for this there are 2 options:

  • Make a "t" class attribute
def clicked(self):
    self.t = Thread()
    self.t.done.connect(self.done)
    self.t.start()
  • Store the QThread in a container that has a longer life cycle:
class Widget(QtWidgets.QWidget):
    def __init__(self):
        super(Widget, self).__init__()
        btn = QtWidgets.QPushButton('test', parent=self)
        btn.clicked.connect(self.clicked)

        self.container = []

    def clicked(self):
        t = Thread()
        t.done.connect(self.done)
        t.start()
        self.container.append(t)

    # ...
  • Pass it as a parent to "self" but for this it is necessary that Thread allow to receive so you must implement that in the constructor:
class Thread(QThread):
    done = Signal()

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

    # ...

def clicked(self):
    t = Thread(self)
    t.done.connect(self.done)
    t.start()

Upvotes: 2

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