from boto.s3.bucket import Bucket
from boto.s3.connection import S3Connection
from boto.s3.key import Key


s3conn = S3Connection()
bucketname = 'dev-hackathon'
keyname_format = '/hotness/charts/{start}-{end}-{country}-{genre}.json'
keyname = keyname_format.format(
    # ...
)
bucket = Bucket(s3conn, bucketname)
key = Key(bucket, keyname)