Your function should probably be called paintEvent. Then make a QTimer like so:
self.timer = QtCore.QTimer()
self.timer.timeout.connect(self.update)
self.timer.start(60000) #trigger every minute.
That is unless you need to for some reason update something in the backed and not in the front end (in other words the function is not used for drawing. Otherwise it should allmost without question be called paintEvent). Then do:
self.timer.timeout.connect(self.Refresh)