Question

My Django view method is below. I want to pass place_data as a response from an HTTPRequest (within a getJSON call on the client side, but that’s irrelevant to the issue).

I can pass the dictionary fine until I include the event_occurrences, which is doing some behind the scenes work to pass a dictionary of events with start and end times.

def mobile_place_detail(request,place_id):

    callback = request.GET.get('callback', 'callback')
    place = get_object_or_404(Place, pk=place_id)
    event_occurrences = place.events_this_week()

    place_data = {
        'Name': place.name,
        'Street': place.street,
        'City': place.city,
        'State': place.state,
        'Zip': place.zip,
        'Telephone': place.telephone,
        'Lat':place.lat,
        'Long':place.long,
        'Events': event_occurrences,
    }
    xml_bytes = json.dumps(place_data)

    if callback:
        xml_bytes = '%s(%s)' % (callback, xml_bytes)
    print xml_bytes

    return HttpResponse(xml_bytes, content_type='application/javascript; charset=utf-8')

Here is the code attempting to do the serialization of the event_occurrences dictionary:

 def events_this_week(self):
    return self.events_this_week_from_datetime( datetime.datetime.now() )

 def events_this_week_from_datetime(self, now):

    event_occurrences = []
    for event in self.event_set.all():
        event_occurrences.extend(event.upcoming_occurrences())

    event_occurrences.sort(key=itemgetter('Start Time'))

    counter = 0
    while counter < len(event_occurrences) and event_occurrences[0]['Start Time'].weekday() < now.weekday():
        top = event_occurrences.pop(0)
        event_occurrences.insert(len(event_occurrences), top)
        counter += 1

    json_serializer = serializers.get_serializer("json")()
     return json_serializer.serialize(event_occurrences, ensure_ascii=False)
    return event_occurrences

The call to event.upcoming_occurrences references the function below:

def upcoming_occurrences(self):

        event_occurrences = []

        monday_time = datetime.datetime.combine(datetime.date.today() + relativedelta(weekday=MO), self.start_time)
        all_times = list(rrule(DAILY, count=7, dtstart=monday_time))

        weekday_names = ('monday', 'tuesday', 'wednesday', 'thursday', 'friday', 'saturday', 'sunday')

        for idx, weekday in enumerate(weekday_names):
            if getattr(self, weekday):
                event_occurrences.append({
                    'Name': self.name,
                    'Start Time': all_times[idx],
                    'End Time': all_times[idx] + datetime.timedelta(minutes=self.duration)
                })

        return event_occurrences

This is giving me the following error:

Exception Type: AttributeError
Exception Value:    'dict' object has no attribute '_meta'

I realize I cannot just call json.dumps() on my event_occurrences object, but can’t figure out how to get around this serialization error (and this is my first time working with serialization in Python). Could someone please give me some direction as how and where the serialization needs to take place?

Thank you in advance!

UPDATE: Added function calls to help with clarity of question. Please see above.

Answer 1

Django’s serialization framework is for QuerySets, not dicts. If you want to just dump a dictionary to JSON, just use json.dumps. It can easily be made to serialize objects by passing in a custom serialization class – there’s one included with Django that deals with datetimes already:

from django.core.serializers.json import DjangoJSONEncoder
json.dumps(mydict, cls=DjangoJSONEncoder)