Reverse for 'A' with arguments '('B',)' not found?

Question

Django

Hello. I don't understand how to set the url to get to the product page.

urls.py

from django.conf.urls import include
from django.contrib import admin
admin.autodiscover()
from django.conf.urls.static import static
from django.contrib.staticfiles.urls import staticfiles_urlpatterns
from django.conf import settings

urlpatterns = [

url(r'^$', app.views.home, name='home'),
url(r'^cart/', include('cart.urls', namespace='cart')),
url(r '^goods/', include('app.urls', namespace='app')), this line should open the product page
...

if settings.DEBUG:
urlpatterns += static(settings.MEDIA_URL,
urlpatterns += static(settings.MEDIA_URL, document_root=settings.MEDIA_ROOT)
urlpatterns += staticfiles_urlpatterns()

urls.py is the application file app

from django.conf.urls import url
from . import views

app_name = 'app'

urlpatterns = [
url(r'^$', views.product_list, name='product_list'),
url(r'/', views.product_list,
name='product_list_by_category'
),
url(r '/', views.product_detail,
name='product_detail')
]

models.py

class Category(models.Model):
name = models.CharField(max_length=100, db_index=True)
slug = models.SlugField(max_length=100, unique=True)

class Meta:
verbose_name = 'Category'
verbose_name_plural = 'Categories'

def __str__(self):
return self.name

def get_absolute_url(self):
return reverse('app:product_list_by_category', args=[self.slug])

views.py

def product_list(request , category_slug=None):
category = None
categories = Category.objects.all()
products = Product.objects.filter(available=True)
if category_slug:
category = get_object_or_404(Category, slug=category_slug)
products = products.filter(category =category)
return render(request, 'app/product/list.html',
{
'category': category,
'categories': categories,
'products':products
})

def product_detail(request, id, slug):
product = get_object_or_404(Product, id=id, slug=slug, available=True)
return render(request, 'app/product/detail.html', {'product': product} ) - along this path is the file

Please, explain "on the fingers" how to fix it. I check the topic every half an hour :)

when I write a link like localhost:53331/goods , the



processors error crashes - this is the name of the category in the admin panel