X_train_raw = [{'a': 1}, {'b': 1}, {'c': 1}]
y_train = [('first',), ('second',), ('first', 'second')]
v = DictVectorizer()
X_train = v.fit_transform(X_train_raw)
clf = OneVsRestClassifier(MultinomialNB())
clf.fit(X_train, y_train)
Using scikit-learn classifier inside nltk, multiclass case