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import nltk | |
import pytextrank | |
import re | |
from operator import itemgetter | |
import en_core_web_sm | |
class KeywordExtractor: | |
""" | |
Keyword Extraction on text data | |
Attributes: | |
nlp: An instance English pipeline optimized for CPU for spacy | |
""" | |
def __init__(self): | |
self.nlp = en_core_web_sm.load() | |
self.nlp.add_pipe("textrank") | |
def get_keywords(self, text, max_keywords): | |
""" | |
Extract keywords from text. | |
Parameters: | |
text (str): The user input string to extract keywords from | |
Returns: | |
kws (list): list of extracted keywords | |
""" | |
doc = self.nlp(text) | |
kws = [i.text for i in doc._.phrases[:max_keywords]] | |
return kws | |
def get_keyword_indices(self, kws, text): | |
""" | |
Extract keywords from text. | |
Parameters: | |
kws (list): list of extracted keywords | |
text (str): The user input string to extract keywords from | |
Returns: | |
keyword_indices (list): list of indices for keyword boundaries in text | |
""" | |
keyword_indices = [] | |
for s in kws: | |
indices = [[m.start(), m.end()] for m in re.finditer(re.escape(s), text)] | |
keyword_indices.extend(indices) | |
return keyword_indices | |
def merge_overlapping_indices(self, keyword_indices): | |
""" | |
Merge overlapping keyword indices. | |
Parameters: | |
keyword_indices (list): list of indices for keyword boundaries in text | |
Returns: | |
keyword_indices (list): list of indices for keyword boundaries in with overlapping combined | |
""" | |
# Sort the array on the basis of start values of intervals. | |
keyword_indices.sort() | |
stack = [] | |
# insert first interval into stack | |
stack.append(keyword_indices[0]) | |
for i in keyword_indices[1:]: | |
# Check for overlapping interval, | |
# if interval overlap | |
if (stack[-1][0] <= i[0] <= stack[-1][-1]) or (stack[-1][-1] == i[0]-1): | |
stack[-1][-1] = max(stack[-1][-1], i[-1]) | |
else: | |
stack.append(i) | |
return stack | |
def merge_until_finished(self, keyword_indices): | |
""" | |
Loop until no overlapping keyword indices left. | |
Parameters: | |
keyword_indices (list): list of indices for keyword boundaries in text | |
Returns: | |
keyword_indices (list): list of indices for keyword boundaries in with overlapping combined | |
""" | |
len_indices = 0 | |
while True: | |
# Merge overlapping indices | |
merged = self.merge_overlapping_indices(keyword_indices) | |
# Check to see if merging reduced number of annotation indices | |
# If merging did not reduce list return final indicies | |
if len_indices == len(merged): | |
out_indices = sorted(merged, key=itemgetter(0)) | |
return out_indices | |
else: | |
len_indices = len(merged) | |
def get_annotation(self, text, keyword_indices): | |
""" | |
Create text annotation for extracted keywords. | |
Parameters: | |
keyword_indices (list): list of indices for keyword boundaries in text | |
Returns: | |
annotation (list): list of tuples for generating html | |
""" | |
# Turn list to numpy array | |
arr = list(text) | |
# Loop through indices in list and insert delimeters | |
for idx in sorted(keyword_indices, reverse=True): | |
arr.insert(idx[0], "<kw>") | |
arr.insert(idx[1]+1, "<!kw> <kw>") | |
# join array | |
joined_annotation = ''.join(arr) | |
# split array on delimeter | |
split = joined_annotation.split('<kw>') | |
# Create annotation for keywords in text | |
annotation = [(x.replace('<!kw> ', ''), "KEY", "#26aaef") if "<!kw>" in x else x for x in split] | |
return annotation | |
def generate(self, text, max_keywords): | |
""" | |
Create text annotation for extracted keywords. | |
Parameters: | |
text (str): The user input string to extract keywords from | |
max_keywords (int): Limit on number of keywords to generate | |
Returns: | |
annotation (list): list of tuples for generating html | |
kws (list): list of extracted keywords | |
""" | |
kws = self.get_keywords(text, max_keywords) | |
indices = list(self.get_keyword_indices(kws, text)) | |
if indices: | |
indices_merged = self.merge_until_finished(indices) | |
annotation = self.get_annotation(text, indices_merged) | |
else: | |
annotation = None | |
return annotation, kws | |