如何安全退出 pyqt 应用程序 python

Question

I have a pyqt5 project. I am starting the window in full screen mode. It is working but because it full screen so I cannot click on x button to close it so I have to press alt-f4 to close it. It works fine but now I have another class running in the project due to which when I press alt-f4 , it closes the window but still looks the thread didnt closed due to which it stays in the terminal. Below is the code:

class RecognizeFaceInFrame(Thread):

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

        self.get_face_name = False
        self.stop_face_thread = False

    def recognize_face_frame(self):
        try:
            if self.get_face_name:
                #SOME CODE
            time.sleep(1)
        except Exception as e:
            print("Exception occurred in recognize face {}".format(e))

    def run(self):
        while not self.stop_face_thread:
            self.recognize_face_frame()

class TRIANGLE(QMainWindow, Ui_MainWindow):
    def __init__(self):
        # SOME CODE
        self.showFullScreen()

        self.timer = QTimer()
        self.timer.timeout.connect(self.view_cam)
        self.timer.start(20)
        self.frame_count = 0

        self.face_recog_thread = RecognizeFaceInFrame()  
        self.face_recog_thread.start()

    def __del__(self):
        self.timer.stop()
        self.face_recog_thread.stop_face_thread = True

    def view_cam(self):
        # SOME CODE


app = QApplication(sys.argv)
app.setStyle('Windows')
main_window = TRIANGLE()
main_window.show()
sys.exit(app.exec_())

I have a class RecognizeFaceInFrame which I am initializing in __init__ in TRIANGLE class. Function recognize_face_frame will start execution if we set get_face_name to True . If we set stop_face_thread to True , this thread will close automatically and thus I have put this in __del__ of TRAINGLE but when I am pressing alt-f4 it doesn't closes. Can anyone please help me understand what I should do here to safely close all the threads and application. Please help. Thanks

Answer 1

How about using closeEvent ?

Classes inheriting Qt modules are removed by Qt's own garbage collector - at least link says so. Therefore, UI Object is not immediately deleted.

Change PySide2 to PyQt and try this. Function closeEvent will run as soon as you hit alt+f4. Until then, thread will keep printing out message to console.

from PySide2.QtWidgets import QWidget, QApplication, QTextEdit, QVBoxLayout
from PySide2.QtGui import QCloseEvent
from threading import Thread
import sys
import time


class TestThread(Thread):

    def __init__(self):
        super().__init__()
        self.stop_thread = False

    def run(self):
        while not self.stop_thread:
            print("I'm alive!")
            time.sleep(1)

        print("Dead! Not a big surprise.")


class MainWindow(QWidget):
    def __init__(self):
        super(MainWindow, self).__init__()

        self.test_thread = TestThread()
        self.test_thread.start()

    def closeEvent(self, event:QCloseEvent):
        self.test_thread.stop_thread = True



if __name__ == '__main__':
    app = QApplication(sys.argv)
    window = MainWindow()
    window.show()
    sys.exit(app.exec_())

Result:

I'm alive!
I'm alive!
I'm alive!
Dead. Not a big surprise.

Process finished with exit code -1

Answer 2

You can also use the aboutToQuit signal from QApplication. Just connect it to your cleanup methods. See docs.