class UpdateAPIView

    def _allowed_methods(self):
        return [m.upper() for m in self.http_method_names if hasattr(self, m)]

    def check_object_permissions(self, request, obj):
        """
        Check if the request should be permitted for a given object.
        Raises an appropriate exception if the request is not permitted.
        """
        for permission in self.get_permissions():
            if not permission.has_object_permission(request, self, obj):
                self.permission_denied(request)

    def check_permissions(self, request):
        """
        Check if the request should be permitted.
        Raises an appropriate exception if the request is not permitted.
        """
        for permission in self.get_permissions():
            if not permission.has_permission(request, self):
                self.permission_denied(request)

    def check_throttles(self, request):
        """
        Check if request should be throttled.
        Raises an appropriate exception if the request is throttled.
        """
        for throttle in self.get_throttles():
            if not throttle.allow_request(request, self):
                self.throttled(request, throttle.wait())

    def filter_queryset(self, queryset):
        """
        Given a queryset, filter it with whichever filter backend is in use.

        You are unlikely to want to override this method, although you may need
        to call it either from a list view, or from a custom `get_object`
        method if you want to apply the configured filtering backend to the
        default queryset.
        """
        for backend in self.get_filter_backends():
            queryset = backend().filter_queryset(self.request, queryset, self)
        return queryset

    def finalize_response(self, request, response, *args, **kwargs):
        """
        Returns the final response object.
        """
        # Make the error obvious if a proper response is not returned
        assert isinstance(response, HttpResponseBase), (
            'Expected a `Response`, `HttpResponse` or `HttpStreamingResponse` '
            'to be returned from the view, but received a `%s`'
            % type(response)
        )

        if isinstance(response, Response):
            if not getattr(request, 'accepted_renderer', None):
                neg = self.perform_content_negotiation(request, force=True)
                request.accepted_renderer, request.accepted_media_type = neg

            response.accepted_renderer = request.accepted_renderer
            response.accepted_media_type = request.accepted_media_type
            response.renderer_context = self.get_renderer_context()

        for key, value in self.headers.items():
            response[key] = value

        return response

    def get_authenticate_header(self, request):
        """
        If a request is unauthenticated, determine the WWW-Authenticate
        header to use for 401 responses, if any.
        """
        authenticators = self.get_authenticators()
        if authenticators:
            return authenticators[0].authenticate_header(request)

    def get_authenticators(self):
        """
        Instantiates and returns the list of authenticators that this view can use.
        """
        return [auth() for auth in self.authentication_classes]

    def get_content_negotiator(self):
        """
        Instantiate and return the content negotiation class to use.
        """
        if not getattr(self, '_negotiator', None):
            self._negotiator = self.content_negotiation_class()
        return self._negotiator

    def get_filter_backends(self):
        """
        Returns the list of filter backends that this view requires.
        """
        if self.filter_backends is None:
            filter_backends = []
        else:
            # Note that we are returning a *copy* of the class attribute,
            # so that it is safe for the view to mutate it if needed.
            filter_backends = list(self.filter_backends)

        if not filter_backends and self.filter_backend:
            warnings.warn(
                'The `filter_backend` attribute and `FILTER_BACKEND` setting '
                'are deprecated in favor of a `filter_backends` '
                'attribute and `DEFAULT_FILTER_BACKENDS` setting, that take '
                'a *list* of filter backend classes.',
                DeprecationWarning, stacklevel=2
            )
            filter_backends = [self.filter_backend]

        return filter_backends

    def get_format_suffix(self, **kwargs):
        """
        Determine if the request includes a '.json' style format suffix
        """
        if self.settings.FORMAT_SUFFIX_KWARG:
            return kwargs.get(self.settings.FORMAT_SUFFIX_KWARG)

    def get_object(self, queryset=None):
        """
        Returns the object the view is displaying.

        You may want to override this if you need to provide non-standard
        queryset lookups.  Eg if objects are referenced using multiple
        keyword arguments in the url conf.
        """
        # Determine the base queryset to use.
        if queryset is None:
            queryset = self.filter_queryset(self.get_queryset())
        else:
            pass  # Deprecation warning

        # Perform the lookup filtering.
        # Note that `pk` and `slug` are deprecated styles of lookup filtering.
        lookup_url_kwarg = self.lookup_url_kwarg or self.lookup_field
        lookup = self.kwargs.get(lookup_url_kwarg, None)
        pk = self.kwargs.get(self.pk_url_kwarg, None)
        slug = self.kwargs.get(self.slug_url_kwarg, None)

        if lookup is not None:
            filter_kwargs = {self.lookup_field: lookup}
        elif pk is not None and self.lookup_field == 'pk':
            warnings.warn(
                'The `pk_url_kwarg` attribute is deprecated. '
                'Use the `lookup_field` attribute instead',
                DeprecationWarning
            )
            filter_kwargs = {'pk': pk}
        elif slug is not None and self.lookup_field == 'pk':
            warnings.warn(
                'The `slug_url_kwarg` attribute is deprecated. '
                'Use the `lookup_field` attribute instead',
                DeprecationWarning
            )
            filter_kwargs = {self.slug_field: slug}
        else:
            raise ImproperlyConfigured(
                'Expected view %s to be called with a URL keyword argument '
                'named "%s". Fix your URL conf, or set the `.lookup_field` '
                'attribute on the view correctly.' %
                (self.__class__.__name__, self.lookup_field)
            )

        obj = get_object_or_404(queryset, **filter_kwargs)

        # May raise a permission denied
        self.check_object_permissions(self.request, obj)

        return obj

    def get_object_or_none(self):
        try:
            return self.get_object()
        except Http404:
            if self.request.method == 'PUT':
                # For PUT-as-create operation, we need to ensure that we have
                # relevant permissions, as if this was a POST request.  This
                # will either raise a PermissionDenied exception, or simply
                # return None.
                self.check_permissions(clone_request(self.request, 'POST'))
            else:
                # PATCH requests where the object does not exist should still
                # return a 404 response.
                raise

    def get_paginate_by(self, queryset=None):
        """
        Return the size of pages to use with pagination.

        If `PAGINATE_BY_PARAM` is set it will attempt to get the page size
        from a named query parameter in the url, eg. ?page_size=100

        Otherwise defaults to using `self.paginate_by`.
        """
        if queryset is not None:
            warnings.warn('The `queryset` parameter to `get_paginate_by()` '
                          'is deprecated.',
                          DeprecationWarning, stacklevel=2)

        if self.paginate_by_param:
            try:
                return strict_positive_int(
                    self.request.QUERY_PARAMS[self.paginate_by_param],
                    cutoff=self.max_paginate_by
                )
            except (KeyError, ValueError):
                pass

        return self.paginate_by

    def get_pagination_serializer(self, page):
        """
        Return a serializer instance to use with paginated data.
        """
        class SerializerClass(self.pagination_serializer_class):
            class Meta:
                object_serializer_class = self.get_serializer_class()

        pagination_serializer_class = SerializerClass
        context = self.get_serializer_context()
        return pagination_serializer_class(instance=page, context=context)

    def get_parser_context(self, http_request):
        """
        Returns a dict that is passed through to Parser.parse(),
        as the `parser_context` keyword argument.
        """
        # Note: Additionally `request` and `encoding` will also be added
        #       to the context by the Request object.
        return {
            'view': self,
            'args': getattr(self, 'args', ()),
            'kwargs': getattr(self, 'kwargs', {})
        }

    def get_parsers(self):
        """
        Instantiates and returns the list of parsers that this view can use.
        """
        return [parser() for parser in self.parser_classes]

    def get_permissions(self):
        """
        Instantiates and returns the list of permissions that this view requires.
        """
        return [permission() for permission in self.permission_classes]

    def get_queryset(self):
        """
        Get the list of items for this view.
        This must be an iterable, and may be a queryset.
        Defaults to using `self.queryset`.

        This method should always be used rather than accessing `self.queryset`
        directly, as `self.queryset` gets evaluated only once, and those results
        are cached for all subsequent requests.

        You may want to override this if you need to provide different
        querysets depending on the incoming request.

        (Eg. return a list of items that is specific to the user)
        """
        if self.queryset is not None:
            return self.queryset._clone()

        if self.model is not None:
            warnings.warn(
                'The `.model` attribute on view classes is now deprecated in favor '
                'of the more explicit `serializer_class` and `queryset` attributes.',
                DeprecationWarning, stacklevel=2
            )
            return self.model._default_manager.all()

        error_format = "'%s' must define 'queryset' or 'model'"
        raise ImproperlyConfigured(error_format % self.__class__.__name__)

    def get_renderer_context(self):
        """
        Returns a dict that is passed through to Renderer.render(),
        as the `renderer_context` keyword argument.
        """
        # Note: Additionally 'response' will also be added to the context,
        #       by the Response object.
        return {
            'view': self,
            'args': getattr(self, 'args', ()),
            'kwargs': getattr(self, 'kwargs', {}),
            'request': getattr(self, 'request', None)
        }

    def get_renderers(self):
        """
        Instantiates and returns the list of renderers that this view can use.
        """
        return [renderer() for renderer in self.renderer_classes]

    def get_serializer(self, instance=None, data=None, files=None, many=False,
                       partial=False, allow_add_remove=False):
        """
        Return the serializer instance that should be used for validating and
        deserializing input, and for serializing output.
        """
        serializer_class = self.get_serializer_class()
        context = self.get_serializer_context()
        return serializer_class(instance, data=data, files=files,
                                many=many, partial=partial,
                                allow_add_remove=allow_add_remove,
                                context=context)

    def get_serializer_class(self):
        """
        Return the class to use for the serializer.
        Defaults to using `self.serializer_class`.

        You may want to override this if you need to provide different
        serializations depending on the incoming request.

        (Eg. admins get full serialization, others get basic serialization)
        """
        serializer_class = self.serializer_class
        if serializer_class is not None:
            return serializer_class

        warnings.warn(
            'The `.model` attribute on view classes is now deprecated in favor '
            'of the more explicit `serializer_class` and `queryset` attributes.',
            DeprecationWarning, stacklevel=2
        )

        assert self.model is not None, \
            "'%s' should either include a 'serializer_class' attribute, " \
            "or use the 'model' attribute as a shortcut for " \
            "automatically generating a serializer class." \
            % self.__class__.__name__

        class DefaultSerializer(self.model_serializer_class):
            class Meta:
                model = self.model
        return DefaultSerializer

    def get_serializer_context(self):
        """
        Extra context provided to the serializer class.
        """
        return {
            'request': self.request,
            'format': self.format_kwarg,
            'view': self
        }

    def get_throttles(self):
        """
        Instantiates and returns the list of throttles that this view uses.
        """
        return [throttle() for throttle in self.throttle_classes]

    def get_view_description(self, html=False):
        """
        Return some descriptive text for the view, as used in OPTIONS responses
        and in the browsable API.
        """
        func = self.settings.VIEW_DESCRIPTION_FUNCTION
        return func(self.__class__, html)

    def get_view_name(self):
        """
        Return the view name, as used in OPTIONS responses and in the
        browsable API.
        """
        func = self.settings.VIEW_NAME_FUNCTION
        return func(self.__class__, getattr(self, 'suffix', None))

    def handle_exception(self, exc):
        """
        Handle any exception that occurs, by returning an appropriate response,
        or re-raising the error.
        """
        if isinstance(exc, (exceptions.NotAuthenticated,
                            exceptions.AuthenticationFailed)):
            # WWW-Authenticate header for 401 responses, else coerce to 403
            auth_header = self.get_authenticate_header(self.request)

            if auth_header:
                exc.auth_header = auth_header
            else:
                exc.status_code = status.HTTP_403_FORBIDDEN

        response = self.settings.EXCEPTION_HANDLER(exc)

        if response is None:
            raise

        response.exception = True
        return response

    def initial(self, request, *args, **kwargs):
        """
        Runs anything that needs to occur prior to calling the method handler.
        """
        self.format_kwarg = self.get_format_suffix(**kwargs)

        # Ensure that the incoming request is permitted
        self.perform_authentication(request)
        self.check_permissions(request)
        self.check_throttles(request)

        # Perform content negotiation and store the accepted info on the request
        neg = self.perform_content_negotiation(request)
        request.accepted_renderer, request.accepted_media_type = neg

    def initialize_request(self, request, *args, **kwargs):
        """
        Returns the initial request object.
        """
        parser_context = self.get_parser_context(request)

        return Request(request,
                       parsers=self.get_parsers(),
                       authenticators=self.get_authenticators(),
                       negotiator=self.get_content_negotiator(),
                       parser_context=parser_context)

    def paginate_queryset(self, queryset, page_size=None):
        """
        Paginate a queryset if required, either returning a page object,
        or `None` if pagination is not configured for this view.
        """
        deprecated_style = False
        if page_size is not None:
            warnings.warn('The `page_size` parameter to `paginate_queryset()` '
                          'is deprecated. '
                          'Note that the return style of this method is also '
                          'changed, and will simply return a page object '
                          'when called without a `page_size` argument.',
                          DeprecationWarning, stacklevel=2)
            deprecated_style = True
        else:
            # Determine the required page size.
            # If pagination is not configured, simply return None.
            page_size = self.get_paginate_by()
            if not page_size:
                return None

        if not self.allow_empty:
            warnings.warn(
                'The `allow_empty` parameter is deprecated. '
                'To use `allow_empty=False` style behavior, You should override '
                '`get_queryset()` and explicitly raise a 404 on empty querysets.',
                DeprecationWarning, stacklevel=2
            )

        paginator = self.paginator_class(queryset, page_size,
                                         allow_empty_first_page=self.allow_empty)
        page_kwarg = self.kwargs.get(self.page_kwarg)
        page_query_param = self.request.QUERY_PARAMS.get(self.page_kwarg)
        page = page_kwarg or page_query_param or 1
        try:
            page_number = paginator.validate_number(page)
        except InvalidPage:
            if page == 'last':
                page_number = paginator.num_pages
            else:
                raise Http404(_("Page is not 'last', nor can it be converted to an int."))
        try:
            page = paginator.page(page_number)
        except InvalidPage as exc:
            error_format = _('Invalid page (%(page_number)s): %(message)s')
            raise Http404(error_format % {
                'page_number': page_number,
                'message': str(exc)
            })

        if deprecated_style:
            return (paginator, page, page.object_list, page.has_other_pages())
        return page

    def partial_update(self, request, *args, **kwargs):
        kwargs['partial'] = True
        return self.update(request, *args, **kwargs)

    def patch(self, request, *args, **kwargs):
        return self.partial_update(request, *args, **kwargs)

    def perform_authentication(self, request):
        """
        Perform authentication on the incoming request.

        Note that if you override this and simply 'pass', then authentication
        will instead be performed lazily, the first time either
        `request.user` or `request.auth` is accessed.
        """
        request.user

    def perform_content_negotiation(self, request, force=False):
        """
        Determine which renderer and media type to use render the response.
        """
        renderers = self.get_renderers()
        conneg = self.get_content_negotiator()

        try:
            return conneg.select_renderer(request, renderers, self.format_kwarg)
        except Exception:
            if force:
                return (renderers[0], renderers[0].media_type)
            raise

    def permission_denied(self, request):
        """
        If request is not permitted, determine what kind of exception to raise.
        """
        if not request.successful_authenticator:
            raise exceptions.NotAuthenticated()
        raise exceptions.PermissionDenied()

    def post_delete(self, obj):
        """
        Placeholder method for calling after deleting an object.
        """
        pass

    def post_save(self, obj, created=False):
        """
        Placeholder method for calling after saving an object.
        """
        pass

    def pre_delete(self, obj):
        """
        Placeholder method for calling before deleting an object.
        """
        pass

    def put(self, request, *args, **kwargs):
        return self.update(request, *args, **kwargs)

    def throttled(self, request, wait):
        """
        If request is throttled, determine what kind of exception to raise.
        """
        raise exceptions.Throttled(wait)

    def update(self, request, *args, **kwargs):
        partial = kwargs.pop('partial', False)
        self.object = self.get_object_or_none()

        serializer = self.get_serializer(self.object, data=request.DATA,
                                         files=request.FILES, partial=partial)

        if not serializer.is_valid():
            return Response(serializer.errors, status=status.HTTP_400_BAD_REQUEST)

        try:
            self.pre_save(serializer.object)
        except ValidationError as err:
            # full_clean on model instance may be called in pre_save,
            # so we have to handle eventual errors.
            return Response(err.message_dict, status=status.HTTP_400_BAD_REQUEST)

        if self.object is None:
            self.object = serializer.save(force_insert=True)
            self.post_save(self.object, created=True)
            return Response(serializer.data, status=status.HTTP_201_CREATED)

        self.object = serializer.save(force_update=True)
        self.post_save(self.object, created=False)
        return Response(serializer.data, status=status.HTTP_200_OK)