倒排索引

#-*- coding:utf-8 -*-import osimport jiebaimport reimport sysreload(sys)sys.setdefaultencoding('utf-8')#文件保存在documents——cn_STOP_WORDS = frozenset([    'a', 'about', 'above', 'above', 'across', 'after', 'afterwards', 'again',    'against', 'all'])#可添加停用词def word_split(text):    word_list = []    pattern = re.compile(u'[\u4e00-\u9fa5]+')    jieba_list = list(jieba.cut(text))    time = {}    for i, c in enumerate(jieba_list):        if c in time:  # record appear time            time[c] += 1        else:            time.setdefault(c, 0) != 0        if pattern.search(c):  # if Chinese            word_list.append((len(word_list), (text.index(c, time[c]), c)))            continue        if c.isalnum():  # if English or number            word_list.append((len(word_list), (text.index(c, time[c]), c.lower())))  # include normalize    return word_listdef words_cleanup(words):    cleaned_words = []    for index, (offset, word) in words:  # words-(word index for search,(letter offset for display,word))        if word in _STOP_WORDS:            continue        cleaned_words.append((index, (offset, word)))    return cleaned_wordsdef word_index(text):    words = word_split(text)    words = words_cleanup(words)    return wordsdef inverted_index(text):    inverted = {}    for index, (offset, word) in word_index(text):        locations = inverted.setdefault(word, [])        locations.append((index, offset))    return inverteddef inverted_index_add(inverted, doc_id, doc_index):    for word, locations in doc_index.iteritems():        indices = inverted.setdefault(word, {})        indices[doc_id] = locations    return inverteddef search(inverted, query):    words = [word for _, (offset, word) in word_index(query) if word in inverted]  # query_words_list    results = [set(inverted[word].keys()) for word in words]    # x = map(lambda old: old+1, x)    doc_set = reduce(lambda x, y: x & y, results) if results else []    precise_doc_dic = {}    if doc_set:        for doc in doc_set:            index_list = [[indoff[0] for indoff in inverted[word][doc]] for word in words]            offset_list = [[indoff[1] for indoff in inverted[word][doc]] for word in words]            precise_doc_dic = precise(precise_doc_dic, doc, index_list, offset_list, 1)  # 词组查询            precise_doc_dic = precise(precise_doc_dic, doc, index_list, offset_list, 2)  # 临近查询            precise_doc_dic = precise(precise_doc_dic, doc, index_list, offset_list, 3)  # 临近查询        return precise_doc_dic    else:        return {}def precise(precise_doc_dic, doc, index_list, offset_list, range):    if precise_doc_dic:        if range != 1:            return precise_doc_dic  # 如果已找到词组,不需再进行临近查询    phrase_index = reduce(lambda x, y: set(map(lambda old: old + range, x)) & set(y), index_list)    phrase_index = map(lambda x: x - len(index_list) - range + 2, phrase_index)    if len(phrase_index):        phrase_offset = []        for po in phrase_index:            phrase_offset.append(offset_list[0][index_list[0].index(po)])  # offset_list[0]代表第一个单词的字母偏移list        precise_doc_dic[doc] = phrase_offset    return precise_doc_dicif __name__ == '__main__':    # Build Inverted-Index for documents    inverted = {}    # documents = {}    #    # doc1 = u"开发者可以指定自己自定义的词典，以便包含jieba词库里没有的词"    # doc2 = u"军机处长到底是谁，Python Perl"    #    # documents.setdefault("doc1", doc1)    # documents.setdefault("doc2", doc2)    documents = {}    for filename in os.listdir('documents_cn'):        f = open('documents_cn//' + filename).read()        documents.setdefault(filename.decode('utf-8'), f)        #documents.setdefault(filename.decode('utf-8'), f)    for doc_id, text in documents.iteritems():        doc_index = inverted_index(text)        inverted_index_add(inverted, doc_id, doc_index)    # Print Inverted-Index    for word, doc_locations in inverted.iteritems():        print word, doc_locations    # Search something and print results    queries = ['第三根火柴', 'kindled third', 'again']    for query in queries:        result_docs = search(inverted, query)        print "Search for '%s': %s" % (query, u','.join(result_docs.keys()))  # %s是str()输出字符串%r是repr()输出对象        def extract_text(doc, index):            return documents[doc].decode('utf-8')[index:index + 30].replace('\n', ' ')        if result_docs:            for doc, offsets in result_docs.items():                for offset in offsets:                    print '   - %s...' % extract_text(doc, offset)        else:            print 'Nothing found!'        print