Use boto to copy an S3 key to an RRS key

copy_to_rrs_key.py

# Copy an existing key in an S3 bucket and specify you want to use
# the Reduced Redundancy Storage (RRS) option of S3 for the new copy
import boto

# create connection to S3 service
s3 = boto.connect_s3()

# lookup my existing bucket
bucket = s3.lookup('mybucket')

# lookup the Key you want to copy in the bucket
key = bucket.lookup('nonrrskey')

# create a copy of the key in the same bucket and specify you want to use RRS
key.copy(key.bucket.name, 'rsskey', reduced_redundancy=True)