The NLTK
documentation is rather poor in this integration. The steps I followed were:
Download http://nlp.stanford.edu/software/stanford-postagger-
The error lies in the arguments written for the StanfordNerTagger function.
The first argument should be a model file or the classifier you are using. You can find that file inside the Stanford zip file. For example:
st = StanfordNERTagger('/home/me/stanford/stanford-postagger-full-2015-04-20/classifier/tagger.ser.gz', '/home/me/stanford/stanford-spanish-corenlp-2015-01-08-models.jar')