Is there a ready-to-use English grammar that I can just load it and use in NLTK? I\'ve searched around examples of parsing with NLTK, but it seems like that I have to manual
Use the MaltParser, there you have a pretrained english-grammar, and also some other pretrained languages. And the Maltparser is a dependency parser and not some simple bottom-up, or top-down Parser.
Just download the MaltParser from http://www.maltparser.org/index.html and use the NLTK like this:
import nltk
parser = nltk.parse.malt.MaltParser()