How to make a common view for both creating a new post and editing it in Django

Question

I have made a model for a post and have to make a form to accept that post. I am using the below given view for generating a form both for making a new one and editing one, if it exists.

If the post exists then there will be a valid post_id and I will pick the correct post object and display the form with the fields filled, but if there is no post_id then I will generate a new blank form.

However I am getting an error

• post_form() takes exactly 2 arguments (1 given)

What am I doing wrong?

def post_form(request,post_id):

    context_instance=RequestContext(request)

    if post_id:
        post = get_object_or_404(Post, pk=post_id)    
    else:
        #if the user is authenticated then pass the user object
        if request.user.is_authenticated():    
            post = Post(creator=request.user)
        else:
            post = Post()

    if request.method == 'POST':        
        if 'save' in request.POST:
            form = PostForm(request.POST, instance = post)
            if form.is_valid():
                form.save()
                return redirect(post)

    # Instantiate an empty form with the given user          
    else:
        form = PostForm(instance = post)

    return render_to_response('forum/post.html', {'form':form}, context_instance)

Answer 1

looks like you need a default value for post_id

def post_form(request, post_id=None):
    ...