title: TypeError: coercing to Unicode: need string or buffer, User found
body: <p>i have to crawl last.fm for users (university exercise). I'm new to python and get following error:</p>
  
  <pre><code> Traceback (most recent call last):
    File "crawler.py", line 23, in &lt;module&gt;
      for f in user_.get_friends(limit='200'):
    File "/opt/local/Library/Frameworks/Python.framework/Versions/2.6/lib/python2.6/site-packages/pylast.py", line 2717, in get_friends
      for node in _collect_nodes(limit, self, "user.getFriends", False):
    File "/opt/local/Library/Frameworks/Python.framework/Versions/2.6/lib/python2.6/site-packages/pylast.py", line 3409, in _collect_nodes
      doc = sender._request(method_name, cacheable, params)
    File "/opt/local/Library/Frameworks/Python.framework/Versions/2.6/lib/python2.6/site-packages/pylast.py", line 969, in _request
      return _Request(self.network, method_name, params).execute(cacheable)
    File "/opt/local/Library/Frameworks/Python.framework/Versions/2.6/lib/python2.6/site-packages/pylast.py", line 721, in __init__
      self.sign_it()
    File "/opt/local/Library/Frameworks/Python.framework/Versions/2.6/lib/python2.6/site-packages/pylast.py", line 727, in sign_it
      self.params['api_sig'] = self._get_signature()
    File "/opt/local/Library/Frameworks/Python.framework/Versions/2.6/lib/python2.6/site-packages/pylast.py", line 740, in _get_signature
      string += self.params[name]
  TypeError: coercing to Unicode: need string or buffer, User found
  </code></pre>
  
  <p>i use the pylast lib for crawling. what i want to do:</p>
  
  <p>i want to get a users friends and the friends of the users friends. the error occurs, when i have a for loop in another for loop. here's the code:</p>
  
  <pre><code>network = pylast.get_lastfm_network(api_key = API_KEY, api_secret = API_SECRET, username = username, password_hash = password_hash)
  user = network.get_user("vidarnelson")
  
  friends = user.get_friends(limit='200')
  
  i = 1
  
  for friend in friends:
   user_ = network.get_user(friend)
   print '#%d %s' % (i, friend)
   i = i + 1
  
   for f in user_.get_friends(limit='200'):
    print f
  </code></pre>
  
  <p>any advice?</p>
  
  <p>thanks in advance. regards!</p>