Переходы между формами

class TestWindow(QtGui.QWidget):
    previousBtn = 0b100
    applyBtn = 0b010
    nextBtn = 0b001
 
    def __init__(self, btns, radioButtonsCountInLn=5, parent=None):
        QtGui.QWidget.__init__(self, parent)
        uic.loadUi('ui/testUi.ui', self)
        self.test.setText(self.lines[0])
 
        if btns & TestWindow.previousBtn:
            self.previousBtn.setEnabled(True)
 
        if btns & TestWindow.applyBtn:
            self.applyBtn.setEnabled(True)
 
        if btns & TestWindow.nextBtn:
            self.nextBtn.setEnabled(True)
 
    for i in range(count):
            currLn = i // radioButtonsCountInLn
            currCol = i % radioButtonsCountInLn
            self.gridLayout.addWidget(QtGui.QRadioButton(str(i + 1)), currLn, currCol)
 
class MainScreen(QtGui.QWidget):
 
    def __init__(self, parent=None):
        QtGui.QWidget.__init__(self, parent)
        uic.loadUi('ui/mainScreenUi.ui', self)
        with open('description.txt', encoding='cp1251') as f:
            description = f.read()
        self.label.setText(description)

class TestController(QtGui.QWidget):
 
    def __init__(self, testCount, parent=None):
        QtGui.QWidget.__init__(self, parent)
        self.testCount = testCount
        
        mainScreen = MainScreen(self)
        self.state = 0
 
        mainScreen.startTestBtn.clicked.connect(self.processState)
 
        self.pool = [mainScreen]
 
    def loadTest(self, numberOfTest, btns):
        btns = TestWindow.nextBtn | TestWindow.applyBtn | TestWindow.previousBtn
        with open('tests/test_' + str(numberOfTest) + '.txt', encoding='cp1251') as f:
            text = f.readline()
            self.pool.append(TestWindow(btns))
 
            if btns & TestWindow.nextBtn:
                self.pool[-1].nextBtn.clicked.connect(self.processState)
 
            if btns & TestWindow.previousBtn:
                self.pool[-1].previousBtn.clicked.connect(self.processState)
 
            if btns & TestWindow.applyBtn:
                self.pool[-1].applyBtn.clicked.connect(self.processRes)
          
    def processState(self):
        self.loadTest(1, TestWindow.nextBtn | TestWindow.applyBtn)
 
if __name__ == '__main__':
    app = QtGui.QApplication(sys.argv)
    test = TestController(5)
    test.show()
    
    sys.exit(app.exec_())