pyqt4;主窗口点击菜单加载多文档的问题；新手请教，资料好少啊，为甚么点击没效果

# -*- coding: utf-8 -*-
from PyQt4.QtGui import *
from PyQt4.QtCore import *
import sys
QTextCodec.setCodecForTr(QTextCodec.codecForName("utf8"))
class MainWindow(QMainWindow):
    def __init__(self,parent=None):
        super(MainWindow,self).__init__(parent)
        self.setWindowTitle(self.tr("加载"))
        self.workSpace=QWorkspace()
        self.setCentralWidget(self.workSpace)
        self.window1=QMainWindow()
        self.window1.setWindowTitle(self.tr("窗口1"))

        layoutMenu=self.menuBar().addMenu(self.tr("菜单"))
        arrange=QAction(self.tr("窗口1"),self)
        self.connect(arrange,SIGNAL("triggered()"),self.Display)
        layoutMenu.addAction(arrange)
    def Display(self):
        self.workSpace.addWindow(self.window1)

app=QApplication(sys.argv)
main=MainWindow()
main.show()
app.exec_()