Qt for Python QCoreApplication：如何退出非GUI应用程序

Question

I have a small non-GUI application that basically starts an event loop, connects a signal to a slot, and emits a signal. I would like the slot to stop the event loop and exit the application.

However, the application does not exit.

Does anyone have any ideas on how to exit from the event loop?

Python 3.7.0

Qt for Python (PySide2) 5.12.0

import sys
from PySide2 import QtCore, QtWidgets

class ConsoleTest(QtCore.QObject):
    all_work_done = QtCore.Signal(str)

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

    def run_test(self):
        self.all_work_done.connect(self.stop_test)
        self.all_work_done.emit("foo!")

    @QtCore.Slot(str)
    def stop_test(self, msg):
        print(f"Test is being stopped, message: {msg}")
        # neither of the next two lines will exit the application.
        QtCore.QCoreApplication.quit()
        # QtCore.QCoreApplication.exit(0)
        return

if __name__ == "__main__":
    app = QtCore.QCoreApplication(sys.argv)
    mainwindow = ConsoleTest()
    sys.exit(app.exec_())

Answer 1

When you call app.exec_() you are entering the Qt event loop, but since you are executing the code that call quit() at the moment the object is being initialized, your application will never quit.

I can think of two options to achieve the "exit" process you want to do:

• Just call sys.exit(1) inside the stop_test() instead of a quit or exit call, or
• you use singleShot to quit the application:

import sys
from PySide2 import QtCore, QtWidgets

class ConsoleTest(QtCore.QObject):
    all_work_done = QtCore.Signal(str)

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

    def run_test(self):
        self.all_work_done.connect(self.stop_test)
        self.all_work_done.emit("foo!")

    @QtCore.Slot(str)
    def stop_test(self, msg):
        print(f"Test is being stopped, message: {msg}")
        QtCore.QTimer.singleShot(10, QtCore.qApp.quit)

if __name__ == "__main__":
    app = QtCore.QCoreApplication(sys.argv)
    mainwindow = ConsoleTest()
    sys.exit(app.exec_())