object data editting form

I’m making django app which allow me to study. It has multiple tests with multiple question each. Every question has one correct answer. I’m trying to make form which allow me to edit answer If I made mistake in passing correct answer during making question.

That’s what I have already made:

models.py

class Question(models.Model):

    text = models.CharField(max_length=200, null=True)
    test = models.ForeignKey(Test, on_delete=models.CASCADE)
    created = models.DateTimeField(auto_now_add = True)

    def get_answer(self):
        return self.answer_set.all()

    def __str__(self):
        return self.text

class Answer(models.Model):
    text = models.CharField(max_length=200)
    question = models.ForeignKey(Question, on_delete=models.CASCADE, related_name='parent')
    def __str__(self):
         return self.text

forms.py

class AnswerEditForm(ModelForm):
    class Meta:
        model = Answer
        exclude = ('question',)

views.py

def UpdateAnswerView(request, pk):
    form = AnswerEditForm()

    if request.method == 'POST':
        form = AnswerEditForm(request.POST)
        if form.is_valid():
            obj = form.save(commit=False)
            obj.question = Question.objects.get(id=pk)
            
            obj.save()
            return redirect('home')

    context = {'form':form}
    return render(request, 'exam/update_answer.html', context)

urls.py
urlpatterns = [
    ~some other urls~
    path('answer/edit/<int:pk>/', views.UpdateAnswerView, name='update-answer'), 

]

while I’m trying to edit answer i’m getting Question matching query does not exist. error.
Where did i make mistake ?

>Solution :

Probably pk is None.
it is better you check your pk

def UpdateAnswerView(request, pk):
    form = AnswerEditForm()

    if request.method == 'POST' and pk is not None:
        form = AnswerEditForm(request.POST)
        if form.is_valid():
            obj = form.save(commit=False)
            try:
               obj.question = Question.objects.get(id=pk)
               obj.save()
               return redirect('home')
            except Question.DoesNotExist:
               pass
          

    context = {'form':form}
    return render(request, 'exam/update_answer.html', context)