title: Python NLTK Classifier.train(trainfeats)... ValueError: need more than 1 value to unpack
body: <pre><code>def word_feats(words):
       return dict([(word, True) for word in words])
  
  for tweet in negTweets:
       words = re.findall(r"[\w']+|[.,!?;]", tweet) #splits the tweet into words
       negwords = [(word_feats(words), 'neg')] #tag the words with feature
       negfeats.append(negwords) #add the words to the feature list
  for tweet in posTweets:
       words = re.findall(r"[\w']+|[.,!?;]", tweet)
       poswords = [(word_feats(words), 'pos')]
       posfeats.append(poswords)
  
  negcutoff = len(negfeats)*3/4 #take 3/4ths of the words
  poscutoff = len(posfeats)*3/4
  
  trainfeats = negfeats[:negcutoff] + posfeats[:poscutoff] #assemble the train set
  testfeats = negfeats[negcutoff:] + posfeats[poscutoff:]
  
  classifier = NaiveBayesClassifier.train(trainfeats)
  print 'accuracy:', nltk.classify.util.accuracy(classifier, testfeats)
  classifier.show_most_informative_features()
  </code></pre>
  
  <p>I am getting the following error when running this code...</p>
  
  <pre><code>File "C:\Python27\lib\nltk\classify\naivebayes.py", line 191, in train
  
  for featureset, label in labeled_featuresets:
  
  ValueError: need more than 1 value to unpack
  </code></pre>
  
  <p>The error is coming from the classifier = NaiveBayesClassifier.train(trainfeats) line and I'm not sure why. I have done something like this before, and my trainfeats seams to be in the same format as then... a sample from the format is listed below... </p>
  
  <p>[[({'me': True, 'af': True, 'this': True, 'joy': True, 'high': True, 'hookah': True, 'got': True}, 'pos')]]</p>
  
  <p>what other value does my trainfeats need to create the classifier?<em>emphasized text</em></p>