import sys
from PyQt4 import QtCore, QtGui

class MainWindow(QtGui.QMainWindow):
    def __init__(self, parent=None):
        super(MainWindow, self).__init__(parent)
        self.init_widgets()

    def init_widgets(self):
        mainLayout = QtGui.QGridLayout()

        self.button1 = QtGui.QCommandLinkButton("Test1")
        self.button2 = QtGui.QCommandLinkButton("Test2")
        self.label = QtGui.QLabel("original value")

        mainLayout.addWidget(self.button1, 1, 0)
        mainLayout.addWidget(self.button2, 1, 1)
        mainLayout.addWidget(self.label, 2, 0, 1, 2)

        machine = QtCore.QStateMachine()
        s1 = QtCore.QState(machine)
        s2 = QtCore.QState(machine)
        s3 = QtCore.QState(machine)
        machine.setInitialState(s1)

        s1.assignProperty(self.label, "text", "in state 1")
        s2.assignProperty(self.label, "text", "in state 2")
        s3.assignProperty(self.label, "text", "in state 3")

        t1 = s1.addTransition(self.button1.clicked, s2)
        t2 = s2.addTransition(self.button1.clicked, s3)
        t3 = s3.addTransition(self.button1.clicked, s1)

        machine.start()

        central_widget = QtGui.QWidget()
        central_widget.setLayout(mainLayout)
        self.setCentralWidget(central_widget)

if __name__ == '__main__':
    app = QtGui.QApplication(sys.argv)
    MainWindow = MainWindow()
    MainWindow.show()
    eventLoop = app.exec_()
    sys.exit(eventLoop)