Why do some django videos check for a non-passing variable in the template?

Question

Django

I'm still tinkering with Django for fun, and I've run into a strange thing.
In some manuals, something like the following code works:
views.py

def post_detail(request, year, month, day, post):
    post = get_object_or_404(Post, slug = post, status='published', publish__year = year,
                             publish__month=month, publish__day=day)
    comments = post.comments.filter(active = True)
    if request.method == 'POST':
        comment_form = CommentForm(data=request.POST)
        if comment_form.is_valid():
            new_comment = comment_form.save(commit=False)
            new_comment.post = post
            new_comment.save()
    else:
        comment_form = CommentForm()
  

    return render(request, 'blog/post/detail.html', {'post': post, 'comments': comments, 'comment_form': comment_form})

detail.html

{% if new_comment %}
        <h2>Your comment has been added.</h2>
    {% else %}

In my template, new_comment is always False. Yes, I can pass it to render and assign False where it is not needed.
But why does it work for others?

Answer 1

As far as I know the code is like this:

{% if new_comment %}
        <h2>Your comment has been added.</h2>
{% else %}

Will work correctly in Django template, even if this variable was not passed during rendering. It will just have the None value there.
Perhaps in your manual this variable was added to the template "for the future" and in the next lessons of the manual it will be passed during rendering. Or maybe just a mistake or a stupid copy-paste from some other resource, I can’t guess.

Answer 2

Just forgot to put it in context

Answer 3

Not sure but worth a try

return render(request, 'blog/post/detail.html', locals())