优先队列会对放进队列的元素进行排序，用法。
要对对象重载小于号，也就是def __lt__(self, other):

import queue
class Sentence_similarity():
    def __init__(self,sentence,title_words_set):
        self.sentence = sentence
        self.sentence_words_set = eliminate_stopwords_punctuations(sentence)
        self.title_words_set = title_words_set
        self.similarity_with_title = calc_similarity(self.sentence_words_set, title_words_set)

    def __lt__(self, other):
        return self.similarity_with_title > other.similarity_with_title

similarity_prio_queue = queue.PriorityQueue()
similarity_prio_queue.put(Sentence_similarity(sentence,title_words_set))