r53_bulk.py

from boto import route53

r53 = route53.connect_to_region(region_name='us-east-1')

dev_aws = r53.get_zone('my-domain.local')

with open('hosts') as host:  
    i = 0
    rrs = route53.record.ResourceRecordSets(r53, dev_aws.id)
    for line in host.readlines():
        line = line.strip()
        parts = line.split(',')
        c = rrs.add_change("UPSERT", parts[1], "A")
        c.add_value(parts[0])
        if i >= 3999:
            rrs.commit()
            rrs = route53.record.ResourceRecordSets(r53, dev_aws.id)
            i = 0
        i += 1
    rrs.commit()