From the documentation:
Whoosh is a fast, pure Python search engine library.
The primary design impetus of Whoosh is that it is pure Python. You should be able to use Whoosh anywhere you can use Python, no compiler or Java required.
Like one if its ancestors, Lucene, Whoosh is not really a search engine, it’s a programmer library for creating a search engine .
Practically no important behavior of Whoosh is hard-coded. Indexing of text, the level of information stored for each term in each field, parsing of search queries, the types of queries allowed, scoring algorithms, etc. are all customizable, replaceable, and extensible.
 It would of course be possible to build a turnkey search engine on top of Whoosh, like Nutch and Solr use Lucene.
Haven’t inventoried script based search engines but perhaps I should.
Experiments with indexing/search behaviors might be easier (read more widespread) with scripting languages.