AppEngine Bulkloader generate data during import

I imported a CSV into the datastore and want to generate a field StringListProperty with a custom action during import (e.g. index generation, doing some calculations). I tried to override the put() method of my model like it is d开发者_开发技巧escribed in question Override save, put, get, etc... methods in Google App Engine, but during bulkloader import this has no effect.

look into google.appengine.ext.bulkload.bulkloader_wizard, there isn't a default transformer for list of str/unicode. You have to make your own.