无法关闭Python PyQt4上的对话框

我的程序有一个主窗口,其中包含我的库存系统。我添加了一个对话框窗口,当我单击“添加项目”时会弹出。我能够成功打开对话框窗口,但似乎无法关闭它。

自己关闭() . 它只会关闭我为防止意外退出而创建的消息框,并且不会关闭对话框窗口,除非您使用IDE或任务管理器结束它。

以下是我的代码片段:

主要的py公司

class Main(QtGui.QMainWindow):
    def __init__(self):
        QtGui.QMainWindow.__init__(self)

        self.db = Database()
        self.model = Model(self)
        self.ui = MainWindow_ui()
        self.ui.setupUi(self)
        self.window = Ui_Dialog()

        self.ui.addItem.clicked.connect(lambda : self.start_Form())

    def start_Form(self):
        window = QtGui.QDialog()
        self.window.setupUi(window)
        self.window.show()

def main():
    app = QtGui.QApplication(sys.argv)
    window = Main()
    window.showMaximized()
    sys.exit(app.exec_())

if __name__ == "__main__":
    main()

附加项。py(包含对话框窗口代码)

def getNumber():
    conn = sqlite3.connect('inventory.db')
    c = conn.cursor()
    c.execute('SELECT seq FROM sqlite_sequence')
    itemNumber = c.fetchone()[0]
    return int(itemNumber) + 1

class Ui_Dialog(QtGui.QDialog):
    def __init__(self):
        QtGui.QDialog.__init__(self)
        self.setupUi(self)

    def setupUi(self, Dialog):
        Dialog.setObjectName(_fromUtf8("Dialog"))
        Dialog.resize(413, 382)

        self.buttonBox = QtGui.QDialogButtonBox(Dialog)
        self.buttonBox.setStandardButtons(
            QtGui.QDialogButtonBox.Cancel | QtGui.QDialogButtonBox.Ok | QtGui.QDialogButtonBox.Reset)
        self.buttonBox.accepted.connect(self.accept)
        self.buttonBox.rejected.connect(self.reject)

    def retranslateUi(self, Dialog):    
        self.itemCode.setText(str(getNumber()))

    def accept(self):
        row = self.mapper.currentIndex()
        self.mapper.submit()
        self.main.model.insertRow(row)
        self.mapper.setCurrentIndex(row)

        self.close()

    def reject(self):
        ret = QtGui.QMessageBox.question(None, 'Close request', 'Are you sure you want to quit?',
                                         QtGui.QMessageBox.Yes | QtGui.QMessageBox.No)
        if ret == QtGui.QMessageBox.Yes:
            self.close()
        else:
            pass