title: Fetch data to and from a website
body: <p>I have read the documentation about <a href="http://docs.python.org/2/howto/urllib2.html" rel="nofollow">HOWTO Fetch Internet Resources Using urllib2</a>. But I can't understand how to use the data parameter. The example:</p>
  
  <pre><code>import urllib
  import urllib2
  
  url = 'http://www.someserver.com/cgi-bin/register.cgi'
  values = {'name' : 'Michael Foord',
            'location' : 'Northampton',
            'language' : 'Python' }
  
  data = urllib.urlencode(values)
  req = urllib2.Request(url, data)
  response = urllib2.urlopen(req)
  the_page = response.read()
  </code></pre>
  
  <p>is not working: <code>socket.error: [Errno 104] Connection reset by peer</code></p>
  
  <p>But what I understand from it is that I can name some options/parameters and give them a value. But my question is: <strong>How I know which parameters are in the website? Or how can I know them?</strong></p>
  
  <p>I have "played" with:</p>
  
  <pre><code>response =urllib2.urlopen(url)
  html=response.read() 
  print html
  </code></pre>
  
  <p>To read the website but I didn't succeed to fetch my data after trying some values that I thought they would work. In the website there is a button to choose file, and some radio buttons to select to get an output. <strong>How can I do it?</strong></p>
  
  <p>The webpage I am trying to fetch is <a href="http://genome.crg.es/software/geneid/geneid.html" rel="nofollow">this one</a>.</p>