问关闭和打开新窗口PYQT5

EN

class Window(QWidget):
    def __init__(self,parent = None):
        super().__init__(parent)
        self.title = 'pySim Z-eighty'
        self.left = 0
        self.top = 0
        self.width = 1200
        self.height = 3000
        self.initUI()

    def initUI(self):
        self.setWindowTitle(self.title)
        self.setGeometry(self.left, self.top, self.width, self.height)

        self.button = QPushButton("Z80")
        self.button1 = QPushButton()
        self.button2 = QPushButton()
        self.container =    QWidget()
        self.layout = QGridLayout()
        self.layout.addWidget(self.button1, 1, 0)
        self.layout.addWidget(self.button, 1, 1)
        self.layout.addWidget(self.button2, 1, 2)
        self.container.setLayout(self.layout)
        self.layoutPrincipal = QBoxLayout(0)
        self.layoutPrincipal.addWidget(self.container)
        self.setLayout(self.layoutPrincipal)
        self.button.pressed.connect(self.IniciarInterfaz)

    def IniciarInterfaz(self):
        self.hide()
        app = QApplication(sys.argv)
        ex = mainWindow()
        ex.setStyleSheet("background-color: #fff")
        ex.show()
        sys.exit(app.exec_())

if __name__ == '__main__':
    app = QApplication(sys.argv)
    ex = Window()
    ex.show()
    sys.exit(app.exec_())