how do I create simple yes/no dialog in qgis python plugin?

Question

I'm making a QGIS plugin that processes a dataset. I started with pluginbuilder and have a GUI that allows me to set what to do.

As my plugin is making changes, when it detects a certain threshold of changes I want it to pop up a dialog with the old and new values and ask whether to apply changes or skip. How do I do that?

The basic structure so far:

if abs(oldCount - newCount) > 10:
    ????

Answer 1

Use QMessageBox.question:

from PyQt4 import QtGui
reply = QMessageBox.question(self.iface.mainWindow(), 'Continue?', 
                 'Your message here', QMessageBox.Yes, QMessageBox.No)
if reply == QtGui.QMessageBox.Yes:
    #do something if yes
else:
    #do something if no    

or in console:

from PyQt4 import QtGui
reply = QtGui.QMessageBox.question(iface.mainWindow(), 'Continue?', 
                 'Your message here', QtGui.QMessageBox.Yes, QtGui.QMessageBox.No)

Answer 2

Maxim's answer is great, but now a little outdated. For console try:

from qgis.PyQt.QtWidgets import QMessageBox

promptReply = QMessageBox.question(iface.mainWindow(), 'Prompt', 'Click a button', QMessageBox.Yes, QMessageBox.No)
                 
if promptReply == QMessageBox.Yes:
    print("You clicked yes")
else:
    print("You clicked no")