The folks at CERN wanted a better way to search High Energy Physics fulltext paper repositories and bibliographical databases that produce result set numbers in the multi-millions.  INSPIRE, the that merges the sources' query results, though, is written in Python.  In order to move back and forth as quickly as possible between the two systems, CERN decided among a number of options to embed INSPIRE in Solr. 

The result, MontySolr, utilizes the power of Java and works with any Python applicatio, as well as any C/C++ app that Python understands.  For more information on MontySolr, check this video of Roman Chyla (CERN). 

CPython Embedded in Solr - Search Solution for Python Lovers With the Speed of Native Java, Roman Chyla, CERN from Lucene Revolution on Vimeo.