class VehicleDetails(models.Model):
    vehicle_name = models.CharField(max_length = 255)
    total_shipments = models.CharField(max_length = 255)
    remaining_shipments = models.CharField(max_length = 255)
    status = models.CharField(max_length = 255)
    time = models.DateTimeField( auto_now_add = True, db_index = True)

vehicle_details_obj = VehicleDetails.objects.filter(status = 'open').order_by('-time')
        try:
            vehicle_name = vehicle_details_obj[0].vehicle_name
            remaining_shipments = int(vehicle_details_obj[0].remaining_shipments) - 1
            print remaining_shipments
            vehicle_details_obj[0].remaining_shipments = str(remaining_shipments)
            if remaining_shipments == 99: vehicle_details_obj[0].status = 'close'
            vehicle_details_obj[0].save()
        except :
            vehicle_name = 'NA'