How to identify the subject of a sentence?

Question

Can Python + NLTK be used to identify the subject of a sentence? From what I have learned till now is that a sentence can be broken into a head and its dependents. For e.g.

Answer 1

You can use Spacy.

Code

import spacy
nlp = spacy.load('en')
sent = "I shot an elephant"
doc=nlp(sent)

sub_toks = [tok for tok in doc if (tok.dep_ == "nsubj") ]

print(sub_toks)