class UpdateView

def form_valid(self, form):
    """If the form is valid, save the associated model."""
    self.object = form.save()
    return super().form_valid(form)

def form_valid(self, form):
    """If the form is valid, redirect to the supplied URL."""
    return HttpResponseRedirect(self.get_success_url())

def get(self, request, *args, **kwargs):
    self.object = self.get_object()
    return super().get(request, *args, **kwargs)

def get(self, request, *args, **kwargs):
    """Handle GET requests: instantiate a blank version of the form."""
    return self.render_to_response(self.get_context_data())

def get_context_data(self, **kwargs):
    """Insert the form into the context dict."""
    if 'form' not in kwargs:
        kwargs['form'] = self.get_form()
    return super().get_context_data(**kwargs)

def get_context_data(self, **kwargs):
    """Insert the single object into the context dict."""
    context = {}
    if self.object:
        context['object'] = self.object
        context_object_name = self.get_context_object_name(self.object)
        if context_object_name:
            context[context_object_name] = self.object
    context.update(kwargs)
    return super().get_context_data(**context)

def get_context_data(self, **kwargs):
    kwargs.setdefault('view', self)
    if self.extra_context is not None:
        kwargs.update(self.extra_context)
    return kwargs

def get_form_class(self):
    """Return the form class to use in this view."""
    if self.fields is not None and self.form_class:
        raise ImproperlyConfigured(
            "Specifying both 'fields' and 'form_class' is not permitted."
        )
    if self.form_class:
        return self.form_class
    else:
        if self.model is not None:
            # If a model has been explicitly provided, use it
            model = self.model
        elif getattr(self, 'object', None) is not None:
            # If this view is operating on a single object, use
            # the class of that object
            model = self.object.__class__
        else:
            # Try to get a queryset and extract the model class
            # from that
            model = self.get_queryset().model
        if self.fields is None:
            raise ImproperlyConfigured(
                "Using ModelFormMixin (base class of %s) without "
                "the 'fields' attribute is prohibited." % self.__class__.__name__
            )
        return model_forms.modelform_factory(model, fields=self.fields)

def get_form_class(self):
    """Return the form class to use."""
    return self.form_class

def get_form_kwargs(self):
    """Return the keyword arguments for instantiating the form."""
    kwargs = super().get_form_kwargs()
    if hasattr(self, 'object'):
        kwargs.update({'instance': self.object})
    return kwargs

def get_form_kwargs(self):
    """Return the keyword arguments for instantiating the form."""
    kwargs = {
        'initial': self.get_initial(),
        'prefix': self.get_prefix(),
    }
    if self.request.method in ('POST', 'PUT'):
        kwargs.update({
            'data': self.request.POST,
            'files': self.request.FILES,
        })
    return kwargs

def get_success_url(self):
    """Return the URL to redirect to after processing a valid form."""
    if self.success_url:
        url = self.success_url.format(**self.object.__dict__)
    else:
        try:
            url = self.object.get_absolute_url()
        except AttributeError:
            raise ImproperlyConfigured(
                "No URL to redirect to.  Either provide a url or define"
                " a get_absolute_url method on the Model.")
    return url

def get_success_url(self):
    """Return the URL to redirect to after processing a valid form."""
    if not self.success_url:
        raise ImproperlyConfigured("No URL to redirect to. Provide a success_url.")
    return str(self.success_url)  # success_url may be lazy

def get_template_names(self):
    """
    Return a list of template names to be used for the request. May not be
    called if render_to_response() is overridden. Return the following list:
    * the value of ``template_name`` on the view (if provided)
    * the contents of the ``template_name_field`` field on the
      object instance that the view is operating upon (if available)
    * ``<app_label>/<model_name><template_name_suffix>.html``
    """
    try:
        names = super().get_template_names()
    except ImproperlyConfigured:
        # If template_name isn't specified, it's not a problem --
        # we just start with an empty list.
        names = []
        # If self.template_name_field is set, grab the value of the field
        # of that name from the object; this is the most specific template
        # name, if given.
        if self.object and self.template_name_field:
            name = getattr(self.object, self.template_name_field, None)
            if name:
                names.insert(0, name)
        # The least-specific option is the default <app>/<model>_detail.html;
        # only use this if the object in question is a model.
        if isinstance(self.object, models.Model):
            object_meta = self.object._meta
            names.append("%s/%s%s.html" % (
                object_meta.app_label,
                object_meta.model_name,
                self.template_name_suffix
            ))
        elif getattr(self, 'model', None) is not None and issubclass(self.model, models.Model):
            names.append("%s/%s%s.html" % (
                self.model._meta.app_label,
                self.model._meta.model_name,
                self.template_name_suffix
            ))
        # If we still haven't managed to find any template names, we should
        # re-raise the ImproperlyConfigured to alert the user.
        if not names:
            raise
    return names

def get_template_names(self):
    """
    Return a list of template names to be used for the request. Must return
    a list. May not be called if render_to_response() is overridden.
    """
    if self.template_name is None:
        raise ImproperlyConfigured(
            "TemplateResponseMixin requires either a definition of "
            "'template_name' or an implementation of 'get_template_names()'")
    else:
        return [self.template_name]

def post(self, request, *args, **kwargs):
    self.object = self.get_object()
    return super().post(request, *args, **kwargs)

def post(self, request, *args, **kwargs):
    """
    Handle POST requests: instantiate a form instance with the passed
    POST variables and then check if it's valid.
    """
    form = self.get_form()
    if form.is_valid():
        return self.form_valid(form)
    else:
        return self.form_invalid(form)