title: How do I get a set of grammar rules from Penn Treebank using python & NLTK?
body: <p>I'm fairly new to NLTK and Python. I've been creating sentence parses using the toy grammars given in the examples but I would like to know if it's possible to use a grammar learned from a portion of the Penn Treebank, say, as opposed to just writing my own or using the toy grammars? (I'm using Python 2.7 on Mac)
  Many thanks</p>