BeautifulSoup：如何提取封装在多个 div/span/id 标签中的文本

我需要在此 html 页面末尾的“td”标签中提取数字（0.04）。

      <div class="boxContentInner">
         <table class="values non-zebra">
   <thead>
   <tr>
      <th>Apertura</th>
      <th>Max</th>
      <th>Min</th>
      <th>Variazione giornaliera</th>
      <th class="last">Variazione %</th>
   </tr>
   </thead>
   <tbody>
   <tr>
      <td id="open" class="quaternary-header">2708.46</td>
      <td id="high" class="quaternary-header">2710.20</td>
      <td id="low" class="quaternary-header">2705.66</td>
      <td id="change" class="quaternary-header changeUp">0.99</td>
      <td id="percentageChange" class="quaternary-header last changeUp">0.04</td>
   </tr>
   </tbody>
</table>

      </div>

我在 Python 2.8 中使用 BeautifulSoup 尝试了此代码：

from bs4 import BeautifulSoup 
import requests 

page= requests.get('https://www.ig.com/au/indices/markets-indices/us-spx-500').text 
soup = BeautifulSoup(page, 'lxml') 

percent= soup.find('td',{'id':'percentageChange'}) 
percent2=percent.text


print percent2

结果是 NONE。

错误在哪里？