Show MessageBox on PySide

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()

References
https://pythonbasics.org/pyqt-qmessagebox/
https://www.tutorialspoint.com/pyqt/pyqt_qmessagebox.htm