title: Python scraping xpath not working with specific sites/tables
body: <p>I am having trouble trying to scrape data from a table at the url:</p>
  
  <p><a href="http://economia.uol.com.br/cotacoes/bolsas/indx-bovespa/?intraday&amp;size=600" rel="nofollow noreferrer">http://economia.uol.com.br/cotacoes/bolsas/indx-bovespa/?intraday&amp;size=600</a></p>
  
  <p>It refers to intraday market data.
  Based on previous examples and the xpath tags provided by firebug, I wrote the code below, but both the tr_nodes and td_content return empty lists:</p>
  
  <pre><code>import urllib2
  from lxml import etree
  uol = urllib2.urlopen("http://economia.uol.com.br/cotacoes/bolsas/indx-bovespa/?intraday&amp;size=600")
  t = uol.read()
  html = etree.HTML(t)
  tr_nodes = html.xpath(".//*[@id='main']/table/tbody/tr")
  td_content = [[td.text for td in tr.xpath('td')] for tr in tr_nodes]
  </code></pre>
  
  <p>I read the question below from Stack Overflow:</p>
  
  <p><a href="https://stackoverflow.com/questions/10907469/python-scraping-reuters-site-bad-xpath">python scraping reuters site...bad xpath?</a></p>
  
  <p>and tried its solution adapted to my needs:</p>
  
  <pre><code>import lxml
  import lxml.html
  import lxml.etree
  
  url = 'http://economia.uol.com.br/cotacoes/bolsas/indx-bovespa/?intraday&amp;size=600'
  
  content = lxml.html.parse(url)
  item = content.xpath(".//*[@id='main']/table/tbody/tr/td")
  ticker = [thing.text for thing in item]
  print ticker
  </code></pre>
  
  <p>The same problem occurred.
  In fact, when I tried writing the whole url content to a text file, I could not find the td nodes I wanted to scrape. Could it be a dinamic table/form that cannot be scraped with the libraries I used, or is it just my ignorance?
  Thanks in advance</p>