Example map/reduce mapper fn

mappers.py

import os
import logging
from mapreduce import context
from mapreduce import shuffler
from mapreduce import operation
from mapreduce import mapreduce_pipeline

from google.appengine.ext import db
from google.appengine.api import files
from google.appengine.ext import blobstore


def map_invite_to_export(invite):

    ''' Yield the proper CSV line for an AccountInvite, attached to the corresponding email address. '''

    if not hasattr(invite, 'email') or not hasattr(invite, 'token'):
        logging.error('Invite at key "'+str(invite.key())+'" is missing a token or email. Cannot dump to CSV. Skipping record.')
    else:
        logging.info('Examining invite at key '+str(invite.key())+' with target email '+invite.email+'.')
        yield ",".join(map(lambda x: '"%s"' % str(x), ## Output values to CSV
		        [
		            invite.firstName, 	## "John"
		            invite.lastName, 	## "Doe"
		            ",".join(map(lambda x: x.name, [k for k in filter(lambda y: y is not None and True or False, db.get(invite.locations))])), ## "\"John's Bar\",\"Jane's Bar\""
		            invite.email,		## "john@johnsbar.com"
		            invite.created,
		            invite.used,
		            "".join([			## "http://<serverhost>/account/invite/claim?token=<token>&source=eminvite"
		                        "http://",
		                        os.environ.get('SERVER_HOST', 'packerseverywhere.appspot.com'),
		                        "/",
		                        "/".join(['account', 'invite', 'claim']),
		                        "?",
		                        "&".join(map(lambda x: "=".join(x), [('t', invite.token), ('source', 'eminvite')]))
		                    ])
		        ]
		    ))+"\n"
                                    
                                    
def export_invite_to_csv(email, csvline):
    
    ''' Export mapped invites to a CSV file in the blobstore. '''
    
    logging.info('AccountInvite for '+str(email)+': '+str(csvline))
    yield str(csvline)