Save to S3

settings.py

DEFAULT_FILE_STORAGE = 'storages.backends.s3boto.S3BotoStorage'
AWS_S3_SECURE_URLS = False
AWS_QUERYSTRING_AUTH = False
AWS_S3_ACCESS_KEY_ID = ""
AWS_S3_SECRET_ACCESS_KEY = ""
AWS_STORAGE_BUCKET_NAME = 'bucket_name'
AWS_HEADERS = {
   'Expires': 'Thu, 15 Apr 2010 20:00:00 GMT',
   'Cache-Control': 'max-age=86400',
   'Content-Type': 'text/xml'
}

views.py

from django.core.files.storage import default_storage

def your_view(request):
    xml_contents = 'SITEMAP XML HERE'
    sitemap_url = '/sitemaps/YYYY/MM/DD-sitemap.xml'
    s3_key = default_storage.open(sitemap_url, 'w')
    s3_key.write(xml_contents)
    s3_key.close()