def orders_by_dow(data_frame):
    """ Gives orders_count by day of week.

    :param data_frame: DataFrame containing orders data.
    :return: DataFrame of order_ids count by day of week.
    """
    grouped = data_frame.groupby(['order_dow'], as_index=False)
    # count by column: 'order_id'
    count = grouped.agg({'order_id': 'count'}).rename(
        columns={'order_id': 'order_id_count'})
    count['week_day'] = ['Saturday', 'Sunday', 'Monday', 'Tuesday',
                         'Wednesday', 'Thursday', 'Friday']
    return count