deep = 0;
list = []
def rec(n)
    deep = deep+1
    list.append((deep,n))
    for nn in Node.objects.filter(parent = n):
         rec(nn)
    deep = deep-1

rec(root)

{% for deep, n in list %}
<p style="left-margin:{{deep}}px">{{n}}</p>
{% endfor %}