QuerySet, Object has no attribute id - Django

问题

I'm trying to fetch the id of certain object in django but I keep getting the following error Exception Value: QuerySet; Object has no attribute id. my function in views.py

@csrf_exempt  
def check_question_answered(request):
    userID = request.POST['userID']
    markerID = request.POST['markerID']
    title=request.POST['question']
    m = Marker.objects.get(id=markerID)
    u = App_User.objects.get(id=userID) 
    print userID
    print markerID
    print title
    # userID='1'
    # markerID='1'
    # title='Hello'
    at = AttachedInfo.objects.filter(attachedMarker=m.id, title=title)
    print 'user'
    print u.id
    print 'marker'
    print m.id
    print 'att'
    print at
    #print at.id
    if(Answer.objects.filter(marker=m.id, user=u.id, attachedInfo=at.id)):
        print 'pass'
        return HttpResponse('already answered')
    else:
        print 'not'
        return HttpResponse('not answered yet') 

The error occurs in the if condition in this part (attachedInfo=at.id). I checked that as when I removed it from the condition, everything was working fine.

Here's models.py

class AttachedInfo(models.Model):
    title = models.CharField(max_length=200)
    helpText = models.CharField(max_length=200, null=True, blank=True)
    type = models.CharField(max_length=200)
    attachedMarker = models.ForeignKey(Marker)
    answer1 = models.CharField(max_length=200, null=True, blank=True)
    answer2 = models.CharField(max_length=200, null=True, blank=True)
    answer3 = models.CharField(max_length=200, null=True, blank=True)
    answer4 = models.CharField(max_length=200, null=True, blank=True)
    correctAnswer = models.CharField(max_length=50, null=True, blank=True)
    optionalMessage = models.CharField(max_length=200, null=True, blank=True)
    def __unicode__(self):
        return self.title

class Answer(models.Model):
    user = models.ForeignKey(App_User)
    app = models.ForeignKey(App, null=True, blank=True)
    marker = models.ForeignKey(Marker)
    attachedInfo = models.ForeignKey(AttachedInfo)
    textAnswer = models.CharField(max_length=200, null=True, blank=True)
    mcqAnswer = models.CharField(max_length=200, null=True, blank=True)
    answered = models.BooleanField(default=False)
    def __unicode__(self):
        return self.attachedInfo.title

Any help why I'm getting this error?!

回答1:

this line of code

at = AttachedInfo.objects.filter(attachedMarker=m.id, title=title)

returns a queryset

and you are trying to access a field of it (that does not exist).

what you probably need is

at = AttachedInfo.objects.get(attachedMarker=m.id, title=title)

回答2:

The reason why you are getting the error is because at is a QuerySet ie: a list. You can do something like at[0].id or use get instead of filter to get the at object.

Hope it helps!

回答3:

In most cases you do not want to handle not existing objects like that. Instead of

ad[0].id

use

get_object_or_404(AttachedInfo, attachedMarker=m.id, title=title)

It is the recommended Django shortcut for that.

来源：https://stackoverflow.com/questions/16572569/queryset-object-has-no-attribute-id-django