我正在Selenium Python中检查网页上下拉字段中的选定值。我想打印出选定值。我正在打印下拉字段中的所有值。例如，下拉字段包含以下值的列表：“浮点”、“日期/时间”、“文本字符串”、“整数”例如，所选值为“文本字符串”，当我打印该值时，它会打印出“浮点日期/时间文本字符串整数”
我的代码片段是：

def get_selected_value_from_user_defined_type_dropdown(self, type):
    # Params : the selected value for the user defined type dropdown e.g. Text string
    user_defined_type_dropdown_element = self.get_element(By.XPATH, '//table[@id="data_configuration_edit_data_object_tab_details_tb_fields"]/tbody/tr[1]//td[3]//select')
    print ("------------------------------")
    print user_defined_type_dropdown_element.text
    return user_defined_type_dropdown_element.text

Get Element在我的基类中，实现为：

# returns the element if found
def get_element(self, how, what):
    # params how: By locator type
    # params what: locator value
    try:
        element = self.driver.find_element(by=how, value=what)
    except NoSuchElementException, e:
        print what
        print "Element not found "
        print e
        screenshot_name = how + what + get_datetime_now() # create screenshot name of the name of the element + locator + todays date time.  This way the screenshot name will be unique and be able to save
        self.save_screenshot(screenshot_name)
        raise
    return element

HTML为：

<table id="data_configuration_edit_data_object_tab_details_tb_fields" class="GJPPK2LBJE border" cellspacing="0" __gwtcellbasedwidgetimpldispatchingfocus="true" __gwtcellbasedwidgetimpldispatchingblur="true">
<thead aria-hidden="false">
<colgroup>
<tbody style="">
    <tr class="GJPPK2LBCD GJPPK2LBJD" __gwt_subrow="0" __gwt_row="0">
    <td class="GJPPK2LBBD GJPPK2LBDD GJPPK2LBED GJPPK2LBKD">
    <td class="GJPPK2LBBD GJPPK2LBDD GJPPK2LBKD">
    <td class="GJPPK2LBBD GJPPK2LBDD GJPPK2LBKD">
        <div __gwt_cell="cell-gwt-uid-214" style="outline-style:none;">
            <select tabindex="-1">
                <option value="Floating point">Floating point</option>
                <option value="Date/time">Date/time</option>
                <option selected="selected" value="Text string">Text string</option>
                <option value="Integer">Integer</option>
        </select>
        </div>
    </td>
        <td class="GJPPK2LBBD GJPPK2LBDD GJPPK2LBOD GJPPK2LBKD">
    </tr>
    <tr class="GJPPK2LBCE" __gwt_subrow="0" __gwt_row="1">
</tbody>
<tbody style="display: none;">
<tfoot style="display: none;" aria-hidden="true"/>

如何打印出所选的值？
我尝试使用first_selected_option，但收到以下错误：

Traceback (most recent call last):
  File "C:\Webdriver\ClearCore 501 Regression Test\ClearCore 501 - Regression Test\TestCases\DataObjectsPage_TestCase.py", line 294, in testk_edit_Data_Objects_ACVSEQ_Is_The_Saved_Details_Present
    self.assertTrue(data_objects_edit_page.is_value_saved_from_user_defined_type_dropdown("Text string"), "Data Objects ACVSEQ type drop down does not show the expected saved value. Please see log for details")
  File "C:\Webdriver\ClearCore 501 Regression Test\ClearCore 501 - Regression Test\Pages\data_objects_edit.py", line 140, in is_value_saved_from_user_defined_type_dropdown
    return self.get_selected_value_from_user_defined_type_dropdown(str(value)) == value
  File "C:\Webdriver\ClearCore 501 Regression Test\ClearCore 501 - Regression Test\Pages\data_objects_edit.py", line 133, in get_selected_value_from_user_defined_type_dropdown
    selected_option_element = user_defined_type_dropdown_element.first_selected_option
AttributeError: 'WebElement' object has no attribute 'first_selected_option'

我的代码片段是：

def get_selected_value_from_user_defined_type_dropdown(self, type):
    #Params : the selected value for the user defined type dropdown e.g. Text string
    user_defined_type_dropdown_element = self.get_element(By.XPATH, '//table[@id="data_configuration_edit_data_object_tab_details_tb_fields"]/tbody/tr[1]//td[3]//select')
    selected_option_element = user_defined_type_dropdown_element.first_selected_option
    print ("------------------------------")
    print selected_option_element.text
    return selected_option_element.text

我从这篇文章中得到了Python使用first_selected_option的代码片段：https://sqa.stackexchange.com/questions/12029/how-do-i-work-with-dropdowns-in-selenium-webdriver
为什么first_selected_option不起作用？请问语法是什么？
谢谢，里亚兹