Python: How Close (or exit) Python Process After QMainWindow Dialog is closed

Question

There are two .py files placed in a same folder:

dialog_01.py and dialog_02.py

Both files are copy of each other. Both build a simple QMainWindow dialog window with two buttons: 'Ok' and 'Cancel'.

Clicking 'Ok' button closes a currently opened dialog window and opens another. So if Dialog_01's Ok button is clicked the dialog_01 is closed and dialog_02 is opened. If Dialog_02's Ok button is clicked then dialog_02 is closed and dialog_01 is opened and so on.

EDITED QUESTION:

Closing the dialog box leaves Python process still running at the background (it can be seen in OSX Activity Monitor or Windows Task Manager).

How to make sure the Python process is terminated after the dialog window is closed?

dialog_01.py

import sys, os
from PyQt4 import QtCore, QtGui    
if 'app' not in globals().keys(): app = QtGui.QApplication(sys.argv)

class Dialog_01(QtGui.QMainWindow):
    def __init__(self):
        super(QtGui.QMainWindow,self).__init__()

        myQWidget = QtGui.QWidget()
        myBoxLayout = QtGui.QVBoxLayout()       

        Cancel_button = QtGui.QPushButton("Cancel")
        Cancel_button.clicked.connect(self.Cancel)      
        myBoxLayout.addWidget(Cancel_button) 


        Button_01 = QtGui.QPushButton("Press to close this dialog and open Dialog 02")
        Button_01.clicked.connect(self.callAnotherQMainWindow)
        myBoxLayout.addWidget(Button_01)        

        myQWidget.setLayout(myBoxLayout)
        self.setCentralWidget(myQWidget)
        self.setWindowTitle('Dialog 01')

    def callAnotherQMainWindow(self):
        from dialog_02 import Dialog_02
        self.close()
        self.dialog_02 = Dialog_02()
        self.dialog_02.show()
        self.dialog_02.raise_()

    def Cancel(self):
        self.close()

    def closeEvent(self):
        self.deleteLater()



if __name__ == '__main__':
    dialog_1 = Dialog_01()
    dialog_1.show()
    dialog_1.resize(480,320)
    sys.exit(app.exec_())

dialog_02.py

import sys, os
from PyQt4 import QtCore, QtGui    
if 'app' not in globals().keys(): app = QtGui.QApplication(sys.argv)

class Dialog_02(QtGui.QMainWindow):
    def __init__(self):
        super(QtGui.QMainWindow,self).__init__()

        myQWidget = QtGui.QWidget()
        myBoxLayout = QtGui.QVBoxLayout()

        Cancel_button = QtGui.QPushButton("Cancel")
        Cancel_button.clicked.connect(self.Cancel)      
        myBoxLayout.addWidget(Cancel_button) 


        Button_02 = QtGui.QPushButton("Press to close this dialog 02 and re-open Dialog 01")
        Button_02.clicked.connect(self.callAnotherQMainWindow)
        myBoxLayout.addWidget(Button_02)

        myQWidget.setLayout(myBoxLayout)
        self.setCentralWidget(myQWidget)
        self.setWindowTitle('Dialog 02')

    def callAnotherQMainWindow(self):
        from dialog_01 import Dialog_01
        self.close()
        self.dialog_01 = Dialog_01()
        self.dialog_01.show()
        self.dialog_01.raise_()

    def Cancel(self):
        self.close()

    def closeEvent(self):
        self.deleteLater()


if __name__ == '__main__':
    dialog_2 = Dialog_02()
    dialog_2.show()
    dialog_2.resize(480,320)
    sys.exit(app.exec_())

Answer 1

Override the closeEvent() function of your QtGui.QMainWindow classes like below:

def closeEvent(self, event):
    self.deleteLater()

This seemed to work:

Removing this:

if 'app' not in globals().keys(): app = QtGui.QApplication(sys.argv)

and this:

if __name__ == '__main__':
    dialog_2 = Dialog_02()
    dialog_2.show()
    dialog_2.resize(480,320)
    sys.exit(app.exec_())

...from dialog2 file did the trick.