Django will not redirect to 404 in try except statement

Question

I'm currently in the process of learning the Django library and am stumped because I am receiving a DoesNotExist error (status = 500) instead of a 404 page error, I tried turning debug = False, however all I received was a 500 status page instead.

class CategoryView(generic.ListView):
    model = Category
    template_name = 'rango/category.html'
    allow_empty = False

    try:
        def get_context_data(self, *args, **kwargs):
            context = super(CategoryView, self).get_context_data(*args, **kwargs)
            category_name = decode_url(self.kwargs['category_name_url'])
            category = Category.objects.get(name = category_name)
            pages = Page.objects.filter(category = category)
            context['category'] = category
            context['pages'] = pages
            return context   
    except Category.DoesNotExist:
        raise Http404

Traceback:

DoesNotExist at /rango/category/Perl/

Category matching query does not exist.

Traceback: File "/Library/Python/2.7/site-packages/django/core/handlers/base.py" in get_response 114. response = wrapped_callback(request, *callback_args, **callback_kwargs) File "/Library/Python/2.7/site-packages/django/views/generic/base.py" in view 69. return self.dispatch(request, *args, **kwargs) File "/Library/Python/2.7/site-packages/django/views/generic/base.py" in dispatch 87. return handler(request, *args, **kwargs) File "/Library/Python/2.7/site-packages/django/views/generic/list.py" in get 152. context = self.get_context_data() File "/Users/justahack/Documents/Python/tango_with_django_project/rango/views.py" in get_context_data 47. category = Category.objects.get(name = category_name) File "/Library/Python/2.7/site-packages/django/db/models/manager.py" in get 151. return self.get_queryset().get(*args, **kwargs) File "/Library/Python/2.7/site-packages/django/db/models/query.py" in get 307. self.model._meta.object_name)

Exception Type: DoesNotExist at /rango/category/Perl/ Exception Value: Category matching query does not exist.

Any help is much appreciated.

Answer 1

The problem is that try/except block is outside the method and it cannot catch the exception inside. To fix it, put try/except into the method:

def get_context_data(self, *args, **kwargs):
    context = super(CategoryView, self).get_context_data(*args, **kwargs)
    category_name = decode_url(self.kwargs['category_name_url'])

    # HERE
    try:
        category = Category.objects.get(name = category_name)
    except Category.DoesNotExist:
        raise Http404

    pages = Page.objects.filter(category = category)
    context['category'] = category
    context['pages'] = pages
    return context

Also, there is a nicer way to throw 404 if the object doesn't exist - use get_object_or_404() shortcut:

def get_context_data(self, *args, **kwargs):
    context = super(CategoryView, self).get_context_data(*args, **kwargs)
    category_name = decode_url(self.kwargs['category_name_url'])
    category = get_object_or_404(Category, name = category_name)
    pages = Page.objects.filter(category = category)
    context['category'] = category
    context['pages'] = pages
    return context