import nltk

gram=nltk.parse_cfg("""
    S -> NP VP
    VP -> V
    NP -> N
    V->'dort'
    N -> 'Jean'
    """)

sent = ['Jean','dort']
parser = nltk.ChartParser(gram)
trees = parser.nbest_parse(sent)
for tree in trees:
  print tree
  print tree.node #noeud courant
  for fils in tree:  # pour chaque noeud fils
    print fils