WordNet works fine in NLTK 3.0. You are just accessing the lemmas (and names) in the wrong way. Try this instead:
>>> import nltk
>>> nltk.__version__
'3.0.0'
>>> from nltk.corpus import wordnet as wn
>>> for synset in wn.synsets('dog'):
for lemma in synset.lemmas():
print lemma.name()
dog
domestic_dog
Canis_familiaris
frump
dog
dog
cad
bounder
blackguard
...
synset.lemmas
is a method and does not have a __getitem__()
method (and so is not subscriptable).