draw tree from s expression by nltk

 >>> import nltk
 >>> from nltk.tree import *
 >>> tree2 = Tree.fromstring('(S (NP I) (VP (V enjoyed) (NP my cookie)))')
 >>> tree2.draw()

http://www.monlp.com/2011/12/16/nltk-trees/
http://www.nltk.org/howto/tree.html
http://www.nltk.org/howto/corpus.html#parsed-corpora