Message: u'The given selector btn dropdown-toggle btn-info is either invalid or does not result in a WebElement

html代码:

<html>

    <head>

        <meta http-equiv="content-type" content="text/html;charset=utf-8" />

        <title>button dropdown</title>

        <script type="text/javascript" async="" src="http://ajax.googleapis.com/ajax/libs/jquery/1.9.1/jquery.min.js"></script>

        <link href="http://netdna.bootstrapcdn.com/twitter-bootstrap/2.3.2/css/bootstrap-combined.min.css" rel="stylesheet" />

        <script type="text/javascript">

            $(document).ready(

                function(){

                    $('.dropdown-menu').find('a').first().click(function(){ alert('watir-webdriver is better than selenium-webdriver'); });

                }

            );

        </script>

    </head>

    <body>

        <h3>button dropdown</h3>

        <div class="row-fluid">

            <div class="span3">

                <div class="well">

                    <div class="btn-group">

                        <a class="btn dropdown-toggle btn-info" data-toggle="dropdown" href="#">

                            Info

                            <span class="caret"></span>

                        </a>

                        <ul class="dropdown-menu">

                            <li><a href="#">watir-webdriver</a></li>

                            <li><a href="#">better than</a></li>

                            <li><a href="#">selenium-webdriver</a></li>

                        </ul>

                    </div>

                </div>

            </div>

        </div>

    </body>

    <script src="http://netdna.bootstrapcdn.com/twitter-bootstrap/2.3.2/js/bootstrap.min.js"></script>

</html>

Python 代码:

#coding=utf-8

from selenium import  webdriver

from selenium.webdriver.common.keys import Keys

from time import  sleep

import  os

if 'HTTP_PROXY' in os.environ: del os.environ['HTTP_PROXY']

dr = webdriver.Firefox()

file_path = 'file:///' + os.path.abspath('button_dropdown.html')

dr.get(file_path)

sleep(1)

#

dr.find_element_by_class_name('btn dropdown-toggle btn-info').click()

buttons =dr.find_elements_by_class_name('dropdown-menu')

for btn in buttons:

    if btn.text == 'better than': btn.click()

sleep(1)

dr.quit()

　　错误信息:InvalidSelectorException: Message: u'The given selector btn dropdown-toggle btn-info is either invalid or does not result in a WebElement.

解决办法:

#coding=utf-8

from selenium import  webdriver

from selenium.webdriver.support.ui import  WebDriverWait

from time import  sleep

import  os

if 'HTTP_PROXY' in os.environ: del os.environ['HTTP_PROXY']

dr = webdriver.Firefox()

file_path = 'file:///' + os.path.abspath('button_dropdown.html')

dr.get(file_path)

sleep(1)

#点击下拉菜单

dr.find_element_by_link_text('Info').click()

#找到dropdown-menu父元素

WebDriverWait(dr,10).until(lambda the_driver: the_driver.find_element_by_class_name('dropdown-menu').is_displayed())

#找到better than

menu = dr.find_element_by_class_name('dropdown-menu').find_element_by_link_text('better than')

menu.click()

sleep(3)

dr.quit()