Dependency Parsing in NLP

SpaCy :

spaCy dependency parser provides token properties to navigate the generated dependency parse tree. Using the dep attribute gives the syntactic dependency relationship between the head token and its child token. The syntactic dependency scheme is used from the ClearNLP. The generated parse tree follows all the properties of a tree and each child token has only one head token although a head token can have multiple children. We can obtain the head token with the token.head property and its children by the token.children property. A subtree of a token can also be extracted using the token.subtree property. Similarly, ancestors for a token can be obtained with token.ancestors. To obtain the rightmost and leftmost token of a token’s syntactic descendants the token.right_edge and token.left_edge can be used. It is also worth mentioning that to extract the neighboring token we can use token.nbor. spaCy doesn’t provide an inbuilt tree representation although you can use the NLTK’s tree representation. Here’s a code snippet for it:

def tok_format(tok):
return "_".join([tok.orth_, tok.tag_, tok.dep_])

def to_nltk_tree(node):
if node.n_lefts + node.n_rights > 0:
return Tree(tok_format(node), [to_nltk_tree(child) for child in node.children])
return tok_format(node)

command = "Submit debug logs to project lead today at 9:00 AM"
en_doc = en_nlp(u'' + command)

[to_nltk_tree(sent.root).pretty_print() for sent in en_doc.sents]
head_word = "null"
question = "What films featured the character Popeye Doyle ?"
en_doc = en_nlp(u'' + question)
for sent in en_doc.sents:
for token in sent:
if token.dep == nsubj and (token.pos == NOUN or token.pos == PROPN):
head_word = token.text
elif token.dep == attr and (token.pos == NOUN or token.pos == PROPN):
head_word = token.text
print(question+" ("+head_word+")")



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Shirish Kadam

Shirish Kadam

Product Management | Productivity | Stoicism