In the context of a parent class like a main window, it is easy to pop up a dialog like a message box:
QMessageBox.information(self, "Title", "Here is your informative message")
This pops up the message I want, with parent being self, the widget already open. But what if I want to show such a dialog in the middle of a Python program all by itself (say, to tell them their program has finished running, or whatever), without invoking a parent class?
I tried the following, and the dialog shows, but when I click OK my system hangs for a few seconds, no message is printed, and my Python kernel restarts (with no error message):
import sys
from PyQt5.QtWidgets import QApplication, QMessageBox
app = QApplication(sys.argv)
mess = QMessageBox()
mess.setText("Here is your message")
mess.setStandardButtons(QMessageBox.Ok | QMessageBox.Cancel)
returnValue = mess.exec_()
if returnValue == QMessageBox.Ok:
print("Clicked OK!")
elif returnValue == QMessageBox.Cancel:
print("Cancelled?!")
print("\n\nNow we are done")
When I click Cancel, it seems to work fine. I am not sure what Qt rules I am breaking here. I could just roll my own little popup using a QWidget I suppose.
I am in pyqt5/python 3.7 running in Spyder/iPython. When I run directly from the command line, it actually seems to work, so this could be an iPython or Spyder problem.
The above code was only "broken" when using Spyder, and now works for newer versions of Spyder (versions 4.1+). So it wasn't a PyQt issue at all, ultimately, but an IDE interaction effect.