def freq_dist_words(self):
from nltk import ConditionalFreqDist
from nltk.model import NgramModel
categories = ['rev_neg.pos','rev_pos.pos']
cfd = ConditionalFreqDist((category, word) for category in categories for word in c.ngrams(c.reader.words(category)))
genres = ['rev_neg.pos', 'rev_pos.pos']
modals = ['location','room','size','staff','excellent','poor','good','bad']
print 'neg :', cfd.__getitem__('rev_neg.pos')
print 'pos :', cfd.__getitem__('rev_pos.pos')
