title: selecting attribute values from lxml
body: <p>I want to use an xpath expression to get the value of an attribute.</p>
  
  <p>I expected the following to work</p>
  
  <pre><code>from lxml import etree
  
  for customer in etree.parse('file.xml').getroot().findall('BOB'):
      print customer.find('./@NAME')
  </code></pre>
  
  <p>but this gives an error :</p>
  
  <pre><code>Traceback (most recent call last):
    File "bob.py", line 22, in &lt;module&gt;
      print customer.find('./@ID')
    File "lxml.etree.pyx", line 1409, in lxml.etree._Element.find (src/lxml/lxml.etree.c:39972)
    File "/usr/local/lib/python2.7/dist-packages/lxml/_elementpath.py", line 272, in find
      it = iterfind(elem, path, namespaces)
    File "/usr/local/lib/python2.7/dist-packages/lxml/_elementpath.py", line 262, in iterfind
      selector = _build_path_iterator(path, namespaces)
    File "/usr/local/lib/python2.7/dist-packages/lxml/_elementpath.py", line 246, in _build_path_iterator
      selector.append(ops[token[0]](_next, token))
  KeyError: '@'
  </code></pre>
  
  <p>Am I wrong to expect this to work?</p>