title: Scraping dynamic html fields with lxml
body: <p>I have been trying to scrape a dynamic field of an HTML page using <code>lxml</code>
  The code is pretty simple and is below:</p>
  
  <pre><code>from lxml import html
  import requests
  page = requests.get('http://www.airmilescalculator.com/distance/blr-to-cdg/')
  tree = html.fromstring(page.content)
  miles = tree.xpath('//input[@class="distanceinput2"]/text()')
  print miles
  </code></pre>
  
  <p>The result that I derive is just an empty list <code>[]</code>
  The result is expected to be a number in the list.
  However I am able to scrape static fields of the same page.</p>
  
  <p>Thanks in advance for the help.</p>