lex_rank_L12.py

import numpy, nltk
nltk.download('punkt')


from harvesttext import HarvestText
from lex_rank_util import degree_centrality_scores, find_siblings_by_index
from sentence_transformers import SentenceTransformer, util


class LexRankL12(object):
    def __init__(self):
        self.model = SentenceTransformer('paraphrase-multilingual-MiniLM-L12-v2')
        self.ht = HarvestText()

    def find_central(self, content: str, num=10, siblings=0):
        if self.contains_chinese(content):
            sentences = self.ht.cut_sentences(content)
        else:
            sentences = nltk.sent_tokenize(content)
        embeddings = self.model.encode(sentences, convert_to_tensor=True).cpu()

        # Compute the pair-wise cosine similarities
        cos_scores = util.cos_sim(embeddings, embeddings).numpy()

        # Compute the centrality for each sentence
        centrality_scores = degree_centrality_scores(cos_scores, threshold=None)

        # We argsort so that the first element is the sentence with the highest score
        most_central_sentence_indices = numpy.argsort(-centrality_scores)

        central_and_siblings = find_siblings_by_index(sentences, most_central_sentence_indices, siblings, num)
        res = []
        for index in central_and_siblings:
            res.append(sentences[index])
        return res

    def contains_chinese(self, content: str):
        for _char in content:
            if '\u4e00' <= _char <= '\u9fa5':
                return True
        return False