{
    "Contents": [
        {
            "LastModified": "2018-06-15T20:40:28.000Z",
            "ETag": "\"80f71457cb2f2aae8d5183e9b3befda7\"",
            "StorageClass": "STANDARD",
            "Key": "000097-20030605.pdf",
            "Owner": {
                "DisplayName": "bpr-admin",
                "ID": "6822198f40e279e66289724108f3a791719ef9422f72611ca45b0ad7cd5e9d12"
            },
            "Size": 15646
        },
        {
            "LastModified": "2018-06-15T20:40:28.000Z",
            "ETag": "\"dafa3ed3e751f2de9030e99f80133113\"",
            "StorageClass": "STANDARD",
            "Key": "000097-20040317.pdf",
            "Owner": {
                "DisplayName": "bpr-admin",
                "ID": "6822198f40e279e66289724108f3a791719ef9422f72611ca45b0ad7cd5e9d12"
            },
            "Size": 16134
        }, ......

-----------------------------------------------------------------------
import json
from shutil import copyfileobj
sitemap_f   = open('sitemap_test.xml', 'a', encoding = 'utf-8')
index_f     = open('index_test.html', 'a')

sm_header = open('sitemap-header.txt', 'r')
copyfileobj(sm_header, sitemap_f)
close(sm_header)

with open('objects.json') as f:
    data = json.load(f)
    objects = data['Contents']
    for object in objects:
        loc = '<loc>' + object['Key'] + '</loc>'
        mod = '<lastmod>' + object['LastModified'] + '</lastmod>'
        sitemap_f.writelines(['<url>','\t' + loc,'\t' + mod,'\t' + '<changefreq>monthly</changefreq>','\t' + '<priority>0.5</priority>','</url>'])