Build a Full Text Search Index in Python

import re
from collections import defaultdict


class SimpleTextIndex:
    def __init__(self):
        self.index = defaultdict(list)
        self.documents = {}

    def add_document(self, doc_id, text):
        self.documents[doc_id] = text
        words = set(re.findall(r'\w+', text.lower()))
        for word in words:
            self.index[word].append(doc_id)

    def search(self, query):
        query_words = re.findall(r'\w+', query.lower())
        if not query_words:
            return []
        result = set(self.index.get(query_words[0], []))
        for word in query_words[1:]:
            result.intersection_update(self.index.get(word, []))
        return sorted(result)


if __name__ == "__main__":
    idx = SimpleTextIndex()
    idx.add_document(1, "The quick brown fox jumps over the lazy dog")
    idx.add_document(2, "Python is a great language for data science")
    idx.add_document(3, "The lazy cat sleeps all day")
    idx.add_document(4, "Data analysis with python and pandas")

    print("Search 'lazy':", idx.search("lazy"))
    print("Search 'python data':", idx.search("python data"))
    print("Search 'quick fox':", idx.search("quick fox"))
    print("Search 'nonexistent':", idx.search("nonexistent"))