Create objects based on date and time

Question

I have an Event model, and each event will have different shows.

class Event(models.Model):
    title = models.CharField(max_length=200)

class Show(models.Model):
    event = models.ForeignKey(Event, on_delete=models.CASCADE)
    date_time = models.DateTimeField(unique=True)

I have another Ticket model. Each ticket should be unique. Meaning each ticket will be unique and relate to a Show and a Seat.

class Ticket(models.Model):
    show = models.ForeignKey(Show)
    seat = models.ForeignKey(Seat)

    class Meta:
        unique_together = ('show', 'seat')

I need to create shows based on the start date and end date provide by the user. Suppose this is a JSON post:

{
    "event_id": 1,
    "start_date": "2018-02-16",
    "end_date": "2018-02-20",
    "time_list": ["11:00 AM", "8:00 PM"]
}

From the above JSON example, I need to create Show starting like this:

# Start with the start_date as the date, and for each time from the time_list
Show.objects.create(
    event = 1,
    date_time = datetime.strptime('2018-02-16 11:00 AM', "%Y-%m-%d %I:%M %p")
)
Show.objects.create(
    event = 1,
    date_time = datetime.strptime('2018-02-16 8:00 PM', "%Y-%m-%d %I:%M %p")
)
# Next date after the start_date, i.e., 16+1 = 17
Show.objects.create(
    event = 1,
    date_time = datetime.strptime('2018-02-17 8:00 PM', "%Y-%m-%d %I:%M %p")
)
.
.
.
# Create Show objects till the end_date and for each time from the time_list
Show.objects.create(
    event = 1,
    date_time = datetime.strptime('2018-02-20 8:00 PM', "%Y-%m-%d %I:%M %p")
)

Right now this is how I am creating Show objects:

def create_show_by_datetime(self, request):
    event_id = request.data['event_id']
    try:
        event = Event.objects.get(id=event_id)
    except Event.DoesNotExist:
        return Response(
            {'error': 'event with id: %s does not exist.' % event_id},
            status=status.HTTP_400_BAD_REQUEST
        )

    start_date = request.data['start_date']
    end_date = request.data['end_date']
    time_list = request.data['time_list']
    date_format = '%Y-%m-%d'
    time_format = "%I:%M %p"
    try:
        datetime.strptime(start_date, date_format)
        datetime.strptime(end_date, date_format)
        for i in range(len(time_list)):
            time = datetime.strptime(time_list[i], time_format)
    except ValueError as e:
        return Response(
            {'error': 'Time was not in a supported format. %s' % e},
            status=status.HTTP_400_BAD_REQUEST
        )

    delta_days = datetime.strptime(end_date, date_format).date() - datetime.strptime(start_date, date_format).date()
    delta_days = delta_days.days + 1
    dt = None
    try:
        with transaction.atomic():
            for i in range(delta_days):
                day = datetime.strptime(start_date, date_format) + timedelta(days=i)
                for i in range(len(time_list)):
                    hrs = datetime.strptime(time_list[i], time_format).hour
                    mins = datetime.strptime(time_list[i], time_format).minute
                    dt = day + timedelta(hours=hrs, minutes=mins)
                    show = Show.objects.create(
                        event=event,
                        date_time=dt
                    )
            return Response({"data": 'Post succesfull'}, status=status.HTTP_201_CREATED)
    except IntegrityError as e:
        return Response(
            {
                'error': "event with date and time already exsits. %s-%s-%s at %s:%s" % (
                    dt.day, dt.month, dt.year, dt.hour, dt.minute),
                'detail': str(e)
            }, status=status.HTTP_400_BAD_REQUEST

But I am hoping there's much more elegant way than how I am doing. I am using python 3, django 2 and django rest frameowork. How can I create Shows with the event, and date_time based on the event_id, start_date, end_date and the time_list?

Answer 1

My approach is a little bit different. You said in the question tag that you are using django-rest-framework.. So where are the serializers? :)

Lets create two serializers, one for user data validation (Because we don't trust the USER!) and one for multi data insert.

I haven't checked the code! But you can use it was an example...

class ShowEventSerializer(serializers.Serializer):
    event_id = serializers.IntegerField()
    start_date = serializers.DateField(required=True)
    end_date = serializers.DateField(required=True)
    time_list = serializers.ListField(
        child=serializers.TimeField()
    )

    class Meta:
        fields = ('event_id', 'start_date', 'end_date', 'time_list')

class ShowSerializer(serializers.Serializer):
    date_time = serializers.DateTimeField()

    class Meta:
        model = Show
        fields = ('event', 'date_time')

Now, with the serializers, we are going to validate the user data and then to create a json data object:

def create_show_by_datetime(self, request):

    show_event_serializer = ShowEventSerializer(data=request.data)
    if not show_event_serializer.is_valid():
        return Response({'error': show_event_serializer.errors},status=status.HTTP_400_BAD_REQUEST)

    event_id = show_event_serializer.data['event_id']
    try:
        event = Event.objects.get(id=event_id)
    except Event.DoesNotExist:
        return Response({'error': 'event with id: %s does not exist.' % event_id},status=status.HTTP_400_BAD_REQUEST)

    start_date = show_event_serializer.data['start_date']
    end_date = show_event_serializer.data['end_date']
    time_list = show_event_serializer.data['time_list']
    date_format = '%Y-%m-%d'
    time_format = "%I:%M %p"

    try:
        datetime.strptime(start_date, date_format)
        datetime.strptime(end_date, date_format)
        for i in range(len(time_list)):
            time = datetime.strptime(time_list[i], time_format)
    except ValueError as e:
        return Response(
            {'error': 'Time was not in a supported format. %s' % e},
            status=status.HTTP_400_BAD_REQUEST
        )

    delta_days = datetime.strptime(end_date, date_format).date() - datetime.strptime(start_date, date_format).date()
    delta_days = delta_days.days + 1
    dt = None
    show_data = []
    for i in range(delta_days):
        day = datetime.strptime(start_date, date_format) + timedelta(days=i)
        for i in range(len(time_list)):
            hrs = datetime.strptime(time_list[i], time_format).hour
            mins = datetime.strptime(time_list[i], time_format).minute
            dt = day + timedelta(hours=hrs, minutes=mins)
            show_data.append({
                "event": event,
                "date_time": dt
            })

    try:
        with transaction.atomic():
            show_serializer = ShowSerializer(data=show_data, many=True)
            if show_serializer.is_valid():
                show_serializer.save()

            return Response({"data": 'Post succesfull'}, status=status.HTTP_201_CREATED)
    except IntegrityError as e:
        return Response(
            {
                'error': "event with date and time already exsits. %s-%s-%s at %s:%s" % (
                    dt.day, dt.month, dt.year, dt.hour, dt.minute),
                'detail': str(e)
            }, status=status.HTTP_400_BAD_REQUEST

So this code is basically the same as yours, with the difference of the way the objects are saved using the DRF. Look the show_data variable.

This solution is just a different way of looking at the question.

GOOD LUCK!

http://www.django-rest-framework.org/api-guide/serializers/

http://www.django-rest-framework.org/api-guide/fields/