How about insert word2vec? This embedding of words in neural network vectors is context sensitive. This can provide a more sophisticated feature set for your classifier.
python word2vec - gensim. Gensim , , . , :
easy_install -U gensim pip install --upgrade gensim.
word2vec
import gensim
documents = [['human', 'interface', 'computer'],
['survey', 'user', 'computer', 'system', 'response', 'time'],
['eps', 'user', 'interface', 'system'],
['system', 'human', 'system', 'eps'],
['user', 'response', 'time'],
['trees'],
['graph', 'trees'],
['graph', 'minors', 'trees'],
['graph', 'minors', 'survey']]
model = gensim.models.Word2Vec(documents, min_count=1)
print model["survey"]
, "", .
Gensim , , .