Prevent multiple form submission for Django Forms

view.py

import hashlib
def register(request):
    if request.method == 'POST':
        request_post = request.POST
        registration_form = RegistrationFormUniqueEmail(request_post)
        hashstring=hashlib.sha1(str(request.POST.get('csrf_token'))) ## This is going  to be unique ! A unique has
        if request.session.get('sesionform')!=hashstring:
			if registration_form.is_valid():
				username =         registration_form.cleaned_data['username']
				email = registration_form.cleaned_data['email']
				password = registration_form.cleaned_data['password']
				new_user = RegistrationProfile.objects.create_inactive_user(username, email, password, "site")
				registration_form = RegistrationFormUniqueEmail()
				return render_to_response('registration/register.html', {'registration_form': registration_form,'messages': "An Email has been sent for your confirmation"})
			else:
				return render_to_response('registration/register.html', {'registration_form': registration_form,'messages':"Error"})
        else:
			return HttpRedirect("/register")

Where is the 'sessionform' set in the session? Do you have to do that manually?