Google app engine datastore tag cloud with python

We have some unstructured textual data in our app engine datastore. I wanted to create a 'one off' tag cloud of one property on a subset of the datastore objects. After a look around, I can't see any framework that will allow me to do this without writing it myself.

The way I had in mind was:

• Write a map (as in map reduce) function to go over every object of the particular type in a datastore,
• Split the text string into words
• For each word increment a counter
• Use the final counts to generate the tag cloud with some third party software (offline - any suggestions here welcome)

As I've never done this before, I was wandering if firstly there is some framework around that does this for me (please) of if not am I approaching it in the right way. i.e please feel free to point out gaping holes in the plan.