An approach to have a weekly report

weekly_report.py

def weekly(query, weeks, initial, final):
    u"""Returns a partitioned result grouped by 7 days.
    query: Initial query
    weeks: Max Number of weeks
    initial: initial part of the week
    final: end part of the week

    You can use like the following:
       previous = weekly(
            my_query, 8, 'validated_at__gt', 'validated_at__lte',
       )
    """
    previous = []
    nextw = -7 * weeks
    week = 0
    while week < weeks:
        ini = now() + timedelta(nextw)
        end = now() + timedelta(nextw + 7)
        previous.insert(0, query.filter(
            **{initial: ini, final: end}
        ).count())
        nextw += 7
        week += 1
    return previous