Boto3 Pagination with for looping through aws accounts

Question

I am having trouble with looping through my 16 accounts, the for loop works in other scripts I have written, but with this one it will only display the last account in accounts users. This is only showing 4 of the 16 to truncate the code a bit. I grab the pagination code from another post on stackoverflow and added this for loop to it. Can anyone help?

 import sys
 import boto3
 **accounts = ["prod","uat","dev","corp"]
  for account in accounts:
         boto3.setup_default_session(profile_name=account)**
 iam = boto3.client("iam")
 marker = None
 while True:
     if marker:
         response_iterator = iam.list_users(
             MaxItems=10,
             Marker=marker
         )
     else:
         response_iterator = iam.list_users(
             MaxItems=20
         )
     print("Next Page : {} ".format(response_iterator['IsTruncated']))
     for user in response_iterator['Users']:
         print(user['UserName'])
     try:
         marker = response_iterator['Marker']
         print(marker)
     except KeyError:
         sys.exit()