from django.conf import settings
from mailsnake import MailSnake
ms = MailSnake(settings.MAILCHIMP_API_KEY)
from django.contrib.auth.models import Group

group_name = 'group-name'
list_id = 'list-id'

group = Group.objects.get(name=group_name)
for user in group.user_set.all():
    result = ms.listSubscribe(id=list_id, email_address=user.email, update_existing=True, double_optin=False)
    print user, result