how to check whether user is logged in or not

I know that the question was already answered, I just want to make a summary of every method for hiding/showing information to non-authenticated users.

1. Login required decorator

If you're dealing with a functional view, you can decorate it like this:

from django.contrib.auth.decorators import login_required

@login_required
def my_view(request):
    pass

This will only show the view to authenticated users. If anonymous, they'll be redirected to the login url (settings.LOGIN_URL)

2. LoginRequiredMixin

from django.contrib.auth.mixins import LoginRequiredMixin

class MyView(LoginRequiredMixin, View):
    login_url = '/login/'
    redirect_field_name = 'redirect_to'

This is for class-based views. From Django documentation:

If a view is using this mixin, all requests by non-authenticated users will be redirected to the login page or shown an HTTP 403 Forbidden error, depending on the raise_exception parameter.

Just like the previous method, you can customize the login_url and redirect_field_name

3. Class-based view method decorator

from django.utils.decorators import method_decorator

class ProtectedView(TemplateView):
    template_name = 'secret.html'

    @method_decorator(login_required)
    def dispatch(self, *args, **kwargs):
        return super().dispatch(*args, **kwargs)

4. HTML templating

Lastly, if you just want to hide some specific HTML block for non-authenticated users, you can wrap it up like this:

{% if user.is_authenticated %}
   <p> Hidden content! </p>
    <!-- You can also access the user data like this -->
   <p> {{ {{ request.user }} }} </p>
{% endif %}

Finally i got the solution that work for me

here it is

Django provides LoginRequiredMixin i used this in my invoicelistview function

from django.contrib.auth.mixins import LoginRequiredMixin, UserPassesTestMixin

class InvoiceListView(LoginRequiredMixin,ListView):
    model = Invoicelist
    template_name = 'invoicedata/home.html'
    context_object_name = 'invoices'

    def get_queryset(self):
        return self.model.objects.all().filter(author=self.request.user).order_by('-date_posted')[:2]

and that's it. Now whenever user logout then it will redirect to login page

In the HTML context, you can do:

{% if user.is_authenticated %} 
        # some arbitary stuff
        <li class="nav-item">
            <a class="nav-link" href="#"><strong>{{ user.username }}</strong></a>
        </li>
{% endif %}

and then in the python context you can do:

from django.contrib.auth.decorators import login_required

@login_required
function stuff():
.....

where @login_required should prefix any function that should only be run by a logged-in user.

Edit: and to address your specific use case, you want to do just:

if request.user.is_authenticated:.