def lemmatize(word):
 lemma = nltk.corpus.wordnet.morphy(word, pos=nltk.corpus.wordnet.VERB)
 if (lemma is not None):
  return lemma
 return word

def lemmatize ( word ) : lemma = nltk . corpus . wordnet . morphy ( word , pos = nltk . corpus . wordnet . VERB ) if ( lemma is not None ) : return lemma return word
use morphy from wordnet to find the base form of verbs .