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I am having issues on trying to figure "DoesNotExist Errors", I have tried to find the right way for manage the no answer results, however I continue having issues on "DoesNotExist" or "Object hast not Attribute DoestNotExists"
from django.http import HttpResponse from django.contrib.sites.models import Site from django.utils import simplejson from vehicles.models import * from gpstracking.models import * def request_statuses(request): data = [] vehicles = Vehicle.objects.filter() Vehicle.vehicledevice_ for vehicle in vehicles: try: vehicledevice = vehicle.vehicledevice_set.get(is_joined__exact = True) imei = vehicledevice.device.imei try: lastposition = vehicledevice.device.devicetrack_set.latest('date_time_process') altitude = lastposition.altitude latitude = lastposition.latitude longitude = lastposition.longitude date_time_process = lastposition.date_time_process.strftime("%Y-%m-%d %H:%M:%S"), date_time_created = lastposition.created.strftime("%Y-%m-%d %H:%M:%S") except Vehicle.vehicledevice.device.DoesNotExist: lastposition = None altitude = None latitude = None longitude = None date_time_process = None date_time_created = None except Vehicle.DoesNotExist: vehicledevice = None imei = '' item = [ vehicle.vehicle_type.name, imei, altitude, "Lat %s Lng %s" % (latitude, longitude), date_time_process, date_time_created, '', '' ] data.append(item) statuses = { "sEcho": 1, "iTotalRecords": vehicles.count(), "iTotalDisplayRecords": vehicles.count(), "aaData": data } json = simplejson.dumps(statuses) return HttpResponse(json, mimetype='application/json') 
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Django Exception Classes The base class for DoesNotExist exceptions. If a query does not return any result, this exception is raised. It raises when the requested field does not exist. This exception is raised by a query if only one object is expected, but multiple objects are returned.
The DoesNotExist exception is raised when an object is not found for the given parameters of a query. Django provides a DoesNotExist exception as an attribute of each model class to identify the class of object that could not be found and to allow you to catch a particular model class with try/except.
This means that your DB is expecting that field to have a value. So when it doesn't you get an error. null. If True, Django will store empty values as NULL in the database. Default is False.
This line
except Vehicle.vehicledevice.device.DoesNotExist means look for device instance for DoesNotExist exception, but there's none, because it's on class level, you want something like
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