Advanced Python Programming

Building an in-memory search index using a hash map

Dictionaries can be used to quickly search for a word in a list of documents, similar to a search engine. In this subsection, we will learn how to build an inverted index based on a dictionary of lists. Let's say we have a collection of four documents:

    docs = ["the cat is under the table",            "the dog is under the table",            "cats and dogs smell roses",            "Carla eats an apple"]

A simple way to retrieve all the documents that match a query is to scan each document and test for the presence of a word. For example, if we want to look up the documents where the word table appears, we can employ the following filtering operation:

    matches = [doc for doc in docs if "table" in doc]

This approach is simple ...