Extract Noun Phrases with Stanza and CoreNLPClient

Question

I am trying to extract noun phrases from sentences using Stanza(with Stanford CoreNLP). This can only be done with the CoreNLPClient module in Stanza.

# Import client module
from stanza.server import CoreNLPClient
# Construct a CoreNLPClient with some basic annotators, a memory allocation of 4GB, and port number 9001
client = CoreNLPClient(annotators=['tokenize','ssplit','pos','lemma','ner', 'parse'], memory='4G', endpoint='http://localhost:9001')

Here is an example of a sentence, and I am using the tregrex function in client to get all the noun phrases. Tregex function returns a dict of dicts in python. Thus I needed to process the output of the tregrex before passing it to the Tree.fromstring function in NLTK to correctly extract the Noun phrases as strings.

pattern = 'NP'
text = "Albert Einstein was a German-born theoretical physicist. He developed the theory of relativity."
matches = client.tregrex(text, pattern) ``

Hence, I came up with the method stanza_phrases which has to loop through the dict of dicts which is the output of tregrex and correctly format for Tree.fromstring in NLTK.

def stanza_phrases(matches):
  Nps = []
  for match in matches:
    for items in matches['sentences']:
      for keys,values in items.items():
        s = '(ROOTn'+ values['match']+')'
        Nps.extend(extract_phrase(s, pattern))
  return set(Nps)

generates a tree to be used by NLTK

from nltk.tree import Tree
def extract_phrase(tree_str, label):
    phrases = []
    trees = Tree.fromstring(tree_str)
    for tree in trees:
        for subtree in tree.subtrees():
            if subtree.label() == label:
                t = subtree
                t = ' '.join(t.leaves())
                phrases.append(t)

    return phrases

Here is my output:

{'Albert Einstein', 'He', 'a German-born theoretical physicist', 'relativity',  'the theory', 'the theory of relativity'}

Is there a way I can make this more code efficient with less number of lines (especially, stanza_phrases and extract_phrase methods)

Asked By: Jesujoba Oluwadara ALABI

||

Source

Answer 1

from stanza.server import CoreNLPClient

# get noun phrases with tregex
def noun_phrases(_client, _text, _annotators=None):
    pattern = 'NP'
    matches = _client.tregex(_text,pattern,annotators=_annotators)
    print("n".join(["t"+sentence[match_id]['spanString'] for sentence in matches['sentences'] for match_id in sentence]))

# English example
with CoreNLPClient(timeout=30000, memory='16G') as client:
    englishText = "Albert Einstein was a German-born theoretical physicist. He developed the theory of relativity."
    print('---')
    print(englishText)
    noun_phrases(client,englishText,_annotators="tokenize,ssplit,pos,lemma,parse")

# French example
with CoreNLPClient(properties='french', timeout=30000, memory='16G') as client:
    frenchText = "Je suis John."
    print('---')
    print(frenchText)
    noun_phrases(client,frenchText,_annotators="tokenize,ssplit,mwt,pos,lemma,parse")

Answered By: StanfordNLPHelp

Answer 2

The Constituent-Treelib does exactly what you want to accomplish, and with very few lines of code.

First install it via: pip install constituent-treelib

Then, perform the following steps:

import spacy
from constituent_treelib import ConstituentTree

text = "Albert Einstein was a German-born theoretical physicist. He developed the theory of relativity."
nlp_pipeline = ConstituentTree.create_pipeline(ConstituentTree.Language.English)
doc = nlp_pipeline(text)
extracted_phrases = []

for sent in doc.sents:
    sentence = sent.text    
    tree = ConstituentTree(sentence, nlp_pipeline)
    extracted_phrases.append(tree.extract_all_phrases())

# --------------------------------------------------------------
# Output of extracted_phrases:

[{'S': ['Albert Einstein was a German - born theoretical physicist .'],
  'ADJP': ['German - born'],
  'VP': ['was a German - born theoretical physicist'],
  'NP': ['Albert Einstein', 'a German - born theoretical physicist']},
 {'S': ['He developed the theory of relativity .'],
  'PP': ['of relativity'],
  'VP': ['developed the theory of relativity'],
  'NP': ['the theory of relativity', 'the theory']}]

Answered By: NeuroMorphing

Extract Noun Phrases with Stanza and CoreNLPClient

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