Not to get side-tracked, but on a related note, it would be nice if there was a python module which defined sets of unicode characters corresponding to different categories (similar to the categories listed here: http://www.fileformat.info/info/unicode/category/index.htm)
That way, for example, if the user wants to categorically ignore ALL mathematical symbols or punctuation marks, they could assign: 

self.wordterminators = unicode_math + unicode_punctuation.
(The + means set union.)

If somebody tried to specify all of them manually, this would be painful.  There are hundreds of punctuation symbols in unicode, for example.  (I suppose most of the time, one does not need to be so thorough.  This feature not really necessary for getting shlex to work.  But I think this would be a easy feature to add.)