python - Django Reverse URL Lookup Template Error -

i'm having bit of trouble reverse url lookups in django.

from template:

<form action="{% url 'blog:save' post.slug %}" method="post">

from urls:

url(r'^post/(?p<slug>\w+)/save/$', views.save, name='save'),

from views:

def save(request, slug):     return httpresponse("not saved.")

error i'm getting:

exception type: noreversematch exception value: reverse 'save' arguments '(u'',)' , keyword arguments '{}' not found.

post.slug variable in template empty string, url requires 1 or more characters (\w+). django builds /post//save/, url invalid.

if need save new post no slug, use optional subpattern in url:

r'^post/(?:(?p<slug>\w+)/)?save/'

Detect