Django AssertionError at url
<p>While learning Django rest framework, I got a <strong>AssertionError at /tasks/1</strong> error </p>

<p><strong>Expected view TaskDetail to be called with a URL keyword argument named "pk". Fix your URL conf, or set the <code>.lookup_field</code> attribute on the view correctly.</strong></p>

<p>My model.py</p>

<pre><code>class Task(models.Model):
    owner=models.ForeignKey('auth.User',related_name='tasks')
    completed=models.BooleanField(default=False)
    title=models.CharField(max_length=100)
    description=models.TextField()
</code></pre>

<p>serializer.py</p>

<pre><code>class TaskSerializer(serializers.ModelSerializer):

class Meta:
    model = Task
    read_only=('owner.username',)
    fields=('title','description','completed','owner.username')
</code></pre>

<p>permission.py</p>

<pre><code>class IsOwnerOrReadOnly(BasePermission):
    def has_object_permission(self, request, view, obj):
        if request.method is SAFE_METHODS:
            return True

        return obj.owner==request.user
</code></pre>

<p>views.py</p>

<pre><code>class TasksMixins(object):
    queryset = Task.objects.all()
    serializer_class=TaskSerializer
    permission_classes=(IsOwnerOrReadOnly,)

    def pre_save(self,obj):
        obj.owner=self.request.user

class TaskList(TasksMixins,ListCreateAPIView):
    pass

class TaskDetail(TasksMixins,RetrieveUpdateDestroyAPIView):
    pass
</code></pre>

<p>Urls.py</p>

<pre><code>urlpatterns = [
    url(r'^$', views.home, name='home'),
    url(r'^tasks/$', views.TaskList.as_view(), name='task_list'),
    url(r'^tasks/(?P&lt;id&gt;[0-9]+)$', views.TaskDetail.as_view(), name='task_detail')
]
</code></pre>

<p>Traceback</p>

<pre><code>Traceback (most recent call last):
  File "/home/amogh/PycharmProjects/env_1.9/local/lib/python2.7/site-packages/django/core/handlers/base.py", line 149, in get_response
    response = self.process_exception_by_middleware(e, request)
  File "/home/amogh/PycharmProjects/env_1.9/local/lib/python2.7/site-packages/django/core/handlers/base.py", line 147, in get_response
    response = wrapped_callback(request, *callback_args, **callback_kwargs)
  File "/home/amogh/PycharmProjects/env_1.9/local/lib/python2.7/site-packages/django/views/decorators/csrf.py", line 58, in wrapped_view
    return view_func(*args, **kwargs)
  File "/home/amogh/PycharmProjects/env_1.9/local/lib/python2.7/site-packages/django/views/generic/base.py", line 68, in view
    return self.dispatch(request, *args, **kwargs)
  File "/home/amogh/PycharmProjects/env_1.9/local/lib/python2.7/site-packages/rest_framework/views.py", line 466, in dispatch
    response = self.handle_exception(exc)
  File "/home/amogh/PycharmProjects/env_1.9/local/lib/python2.7/site-packages/rest_framework/views.py", line 463, in dispatch
    response = handler(request, *args, **kwargs)
  File "/home/amogh/PycharmProjects/env_1.9/local/lib/python2.7/site-packages/rest_framework/generics.py", line 286, in get
    return self.retrieve(request, *args, **kwargs)
  File "/home/amogh/PycharmProjects/env_1.9/local/lib/python2.7/site-packages/rest_framework/mixins.py", line 56, in retrieve
    instance = self.get_object()
  File "/home/amogh/PycharmProjects/env_1.9/local/lib/python2.7/site-packages/rest_framework/generics.py", line 93, in get_object
    (self.__class__.__name__, lookup_url_kwarg)
AssertionError: Expected view TaskDetail to be called with a URL keyword argument named "pk". Fix your URL conf, or set the `.lookup_field` attribute on the view correctly.
</code></pre>

<p>When ever I navigate to the link I get this error</p>

<p>Any help is much appreciated...Thanks in advace</p>

<p><a href="http://i.stack.imgur.com/QO4Qt.png" rel="nofollow">error image</a></p>