Python-сообщество

def show_catalog(request, shop, cat1, cat2):
    cont = RequestContext(request, {})
    if cat2 != None: # зашли в под под раздел
        parent1 = Category.objects.get(id__exact=cat1, shop__exact=shop)
        parent2 = Category.objects.get(id__exact=cat2, shop__exact=shop)
        cont['link_path']=[shop, parent1.name, parent2.name]
        return render_to_response('catalog.html',context_instance=cont)
    elif cat1 != None: # зашли в под раздел
        cat_list = Category.objects.filter(parent_category__exact=cat1, shop__exact=shop)
        cont['cat_list'] = cat_list
        parent1 = Category.objects.get(id__exact=cat1, shop__exact=shop)
        cont['link_path']=[shop, parent1.name]
        cont['shop'] = shop
        return render_to_response('catalog.html',context_instance=cont)
    else: # зашли в корень магазина
        cat_list = Category.objects.filter(parent_category__exact=None, shop__exact=shop)
        cont['cat_list'] = cat_list
        cont['shop'] = shop
        cont['link_path'] = [shop]
        return render_to_response('catalog.html',context_instance=cont)

    url(r'^catalog/(?P<shop>[a-zA-Z0-9]{1,50})/$', 'show_catalog', {'cat1':None, 'cat2':None}, name='catalog'),
    url(r'^catalog/(?P<shop>[a-zA-Z0-9]{1,50})/(?P<cat1>[a-zA-Z0-9]{1,50})/$', 'show_catalog', {'cat2':None}, name='catalog_cat1'),
    url(r'^catalog/(?P<shop>[a-zA-Z0-9]{1,50})/(?P<cat1>[a-zA-Z0-9]{1,50})/(?P<cat2>[a-zA-Z0-9]{1,50})/$', 'show_catalog', name='catalog_cat2'),

            {% for cat in cat_list %}
                <li><a href="{% url catalog_cat1 shop=shop cat1=cat.id %}">{{ cat.name }}</a></li>
            {% endfor %}