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# coding=UTF-8
import nltk
from nltk.corpus import brown
# This is a fast and simple noun phrase extractor (based on NLTK)
# Feel free to use it, just keep a link back to this post
# http://thetokenizer.com/2013/05/09/efficient-way-to-extract-the-main-topics-of-a-sentence/
# Create by Shlomi Babluki
# May, 2013
# This is our fast Part of Speech tagger
#############################################################################
brown_train = brown.tagged_sents(categories='news')
regexp_tagger = nltk.RegexpTagger(
[(r'^-?[0-9]+(.[0-9]+)?$', 'CD'),
(r'(-|:|;)$', ':'),
(r'\'*$', 'MD'),
(r'(The|the|A|a|An|an)$', 'AT'),
(r'.*able$', 'JJ'),
(r'^[A-Z].*$', 'NNP'),
(r'.*ness$', 'NN'),
(r'.*ly$', 'RB'),
(r'.*s$', 'NNS'),
(r'.*ing$', 'VBG'),
(r'.*ed$', 'VBD'),
(r'.*', 'NN')
])
unigram_tagger = nltk.UnigramTagger(brown_train, backoff=regexp_tagger)
bigram_tagger = nltk.BigramTagger(brown_train, backoff=unigram_tagger)
#############################################################################
# This is our semi-CFG; Extend it according to your own needs
#############################################################################
cfg = {}
cfg["NNP+NNP"] = "NNP"
cfg["NN+NN"] = "NNI"
cfg["NNI+NN"] = "NNI"
cfg["JJ+JJ"] = "JJ"
cfg["JJ+NN"] = "NNI"
#############################################################################
class NPExtractor(object):
def __init__(self, sentence):
self.sentence = sentence
# Split the sentence into singlw words/tokens
def tokenize_sentence(self, sentence):
tokens = nltk.word_tokenize(sentence)
return tokens
# Normalize brown corpus' tags ("NN", "NN-PL", "NNS" > "NN")
def normalize_tags(self, tagged):
n_tagged = []
for t in tagged:
if t[1] == "NP-TL" or t[1] == "NP":
n_tagged.append((t[0], "NNP"))
continue
if t[1].endswith("-TL"):
n_tagged.append((t[0], t[1][:-3]))
continue
if t[1].endswith("S"):
n_tagged.append((t[0], t[1][:-1]))
continue
n_tagged.append((t[0], t[1]))
return n_tagged
# Extract the main topics from the sentence
def extract(self):
tokens = self.tokenize_sentence(self.sentence)
tags = self.normalize_tags(bigram_tagger.tag(tokens))
merge = True
while merge:
merge = False
for x in range(0, len(tags) - 1):
t1 = tags[x]
t2 = tags[x + 1]
key = "%s+%s" % (t1[1], t2[1])
value = cfg.get(key, '')
if value:
merge = True
tags.pop(x)
tags.pop(x)
match = "%s %s" % (t1[0], t2[0])
pos = value
tags.insert(x, (match, pos))
break
matches = []
for t in tags:
if t[1] == "NNP" or t[1] == "NNI":
#if t[1] == "NNP" or t[1] == "NNI" or t[1] == "NN":
matches.append(t[0])
return matches
# Main method, just run "python np_extractor.py"
def main():
sentence = "Swayy is a beautiful new dashboard for discovering and curating online content."
np_extractor = NPExtractor(sentence)
result = np_extractor.extract()
print "This sentence is about: %s" % ", ".join(result)
if __name__ == '__main__':
main()

Hey man, can you explain the extract function from line 77. Thanks!

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