src.dackar.similarity.stringSimilarity
======================================

.. py:module:: src.dackar.similarity.stringSimilarity

.. autoapi-nested-parse::

   Lightweight, dependency-free string-similarity measures.

   These are surface (lexical) measures that compare the characters or tokens of
   two strings directly, with no linguistic resources.  They complement the
   WordNet/embedding measures elsewhere in :mod:`dackar.similarity` and make good
   fallbacks when those heavier measures are unavailable.

   Only the standard library is required.



Functions
---------

.. autoapisummary::

   src.dackar.similarity.stringSimilarity.token_jaccard
   src.dackar.similarity.stringSimilarity.trigram_jaccard


Module Contents
---------------

.. py:function:: token_jaccard(text_a, text_b)

   Return the Jaccard index of the two strings' lowercased token sets.

   Tokens are whitespace-separated.  Two empty strings are defined as fully
   similar (1.0); one empty and one non-empty are fully dissimilar (0.0).


.. py:function:: trigram_jaccard(text_a, text_b)

   Return the Jaccard index of the two strings' character-trigram sets.

   Character trigrams give better recall than word Jaccard for short strings
   because they handle partial word matches (e.g. "calibr" in both
   "calibrate" and "calibration") and minor typos (edit distance <= 1 on a
   trigram).  Strings shorter than 3 characters are treated as a single
   "trigram" equal to the whole (lowercased) string.