title: XPath: select tag with empty value
body: <p>How I can find in XPath 1.0 all rows with empty <code>col name="POW"</code>?</p>
  
  <pre><code>&lt;row&gt;
  &lt;col name="WOJ"&gt;02&lt;/col&gt;
  &lt;col name="POW"/&gt;
  &lt;col name="GMI"/&gt;
  &lt;col name="RODZ"/&gt;
  &lt;col name="NAZWA"&gt;DOLNOŚLĄSKIE&lt;/col&gt;
  &lt;col name="NAZDOD"&gt;województwo&lt;/col&gt;
  &lt;col name="STAN_NA"&gt;2011-01-01&lt;/col&gt;
  &lt;/row&gt;
  </code></pre>
  
  <p>I tried many solutions. Few times in Firefox extension XPath Checker selection was ok, but <code>lxml.xpath()</code> says that expression is invalid or just returns no rows.</p>
  
  <p>My Python code:</p>
  
  <pre><code>from lxml import html
  f = open('TERC.xml', 'r')
  page = html.fromstring(f.read())
  for r in page.xpath("//row[col[@name = 'POW' and not(text())]]"):
      print r.text_content()
      print "-------------------------"
  </code></pre>