python pyqt5 QTableWidget 添加右键菜单

def __init__(self):
    super().__init__()
    self.initUI()

def initUI(self):
    self.setWindowTitle("QTableWidget 例子")
    self.resize(500, 300);
    conLayout = QHBoxLayout()
    self.tableWidget = QTableWidget()
    self.tableWidget.setRowCount(5)
    self.tableWidget.setColumnCount(3)
    conLayout.addWidget(self.tableWidget)

    self.tableWidget.setHorizontalHeaderLabels(['姓名', '性别', '体重'])
    self.tableWidget.horizontalHeader().setSectionResizeMode(QHeaderView.Stretch)

    newItem = QTableWidgetItem("张三")
    self.tableWidget.setItem(0, 0, newItem)

    newItem = QTableWidgetItem("男")
    self.tableWidget.setItem(0, 1, newItem)

    newItem = QTableWidgetItem("160")
    self.tableWidget.setItem(0, 2, newItem)
    # 表格中第二行记录
    newItem = QTableWidgetItem("李四")
    self.tableWidget.setItem(1, 0, newItem)

    newItem = QTableWidgetItem("女")
    self.tableWidget.setItem(1, 1, newItem)

    newItem = QTableWidgetItem("170")
    self.tableWidget.setItem(1, 2, newItem)

    self.tableWidget.setContextMenuPolicy(Qt.CustomContextMenu)  ######允许右键产生子菜单
    self.tableWidget.customContextMenuRequested.connect(self.generateMenu)  ####右键菜单
    self.setLayout(conLayout)

def generateMenu(self, pos):
    # rint( pos)
    row_num = -1
    for i in self.tableWidget.selectionModel().selection().indexes():
        row_num = i.row()

    if row_num < 2:
        menu = QMenu()
        item1 = menu.addAction(u"选项一")
        item2 = menu.addAction(u"选项二")
        item3 = menu.addAction(u"选项三")
        action = menu.exec_(self.tableWidget.mapToGlobal(pos))
        if action == item1:
            print('您选了选项一，当前行文字内容是：', self.tableWidget.item(row_num, 0).text(),
                  self.tableWidget.item(row_num, 1).text(), self.tableWidget.item(row_num, 2).text())

        elif action == item2:
            print('您选了选项二，当前行文字内容是：', self.tableWidget.item(row_num, 0).text(),
                  self.tableWidget.item(row_num, 1).text(), self.tableWidget.item(row_num, 2).text())

        elif action == item3:
            print('您选了选项三，当前行文字内容是：', self.tableWidget.item(row_num, 0).text(),
                  self.tableWidget.item(row_num, 1).text(), self.tableWidget.item(row_num, 2).text())
        else:
            return