AniX

def partialize(phrase, shortest=5):
    """Tokenize the string `phrase` argument for all possible sub-strings 
    at least `shortest` length of characters.
    This is a work-around for Google App Engine's Search API not supporting
    partial full-text search (as of time of writing, April 2013


    In case of BBCode-formatted phrase, you should first strip() away all
    BBCode tags before passing the string to this method.

AniX

import datetime
from google.appengine.ext import ndb
# eventually import custom User class here and adjust paths below

# parameter in timedelta() assumes that tokens expire ~3 months after creation:
expiredTokens = User.token_model.query(User.token_model.created <= (datetime.datetime.utcnow() - datetime.timedelta(3*365/12)))

# delete the tokens in bulks of 100:
while expiredTokens.count() > 0:
  keys = expiredTokens.fetch(100, keys_only=True)