MsgBox_test.py

import sys
from PyQt5.QtGui import *
from PyQt5.QtCore import *


def window():
    app = QApplication(sys.argv)
    w = QWidget()
    b = QPushButton(w)
    b.setText("Show message!")

    b.move(50, 50)
    b.clicked.connect(showdialog)
    w.setWindowTitle("PyQt Dialog demo")
    w.show()
    sys.exit(app.exec_())


def showdialog():
    msg = QMessageBox()
    msg.setIcon(QMessageBox.Information)

    msg.setText("This is a message box")
    msg.setInformativeText("This is additional information")
    msg.setWindowTitle("MessageBox demo")
    msg.setDetailedText("The details are as follows:")
    msg.setStandardButtons(QMessageBox.Ok | QMessageBox.Cancel)
    msg.buttonClicked.connect(msgbtn)

    retval = msg.exec_()
    print
    "value of pressed message box button:", retval


def msgbtn(i):
    print
    "Button pressed is:", i.text()


if __name__ == '__main__':
    window()