This feature is documented here:
It is also possible to connect signals by passing a slot as a keyword argument corresponding to the name of the signal when creating an object, or using the pyqtConfigure() method of QObject. For example the following three fragments are equivalent:
act = QtGui.QAction("Action", self)
act.triggered.connect(self.on_triggered)
act = QtGui.QAction("Action", self, triggered=self.on_triggered)
act = QtGui.QAction("Action", self)
act.pyqtConfigure(triggered=self.on_triggered)