Just to add to what @alasdair mentioned, I added re_path as part of the include and it works fine. Here is an example

Add re_path to your import (for django 2.0)

from django.urls import path, re_path

urlpatterns = [
    path('admin/', admin.site.urls),
    re_path(r'^$', home, name='home'),

]

Instead of using ‘re_path’ you can also use ”(empty string) as the first argument of your path(). I have used it and it worked for me.

urlpatterns = [
    path('admin/', admin.site.urls),
    path('',views.index,name='index'),
]

url() is deprecated in newer version of django. So instead of url() use re_path() in your urls file as follows:

from django.urls import path, re_path
from . import views

urlpatterns = [
    #url(r'^(?P<album_id>[0-9]+)/$', views.detail, name='detail'),
    path('', views.index, name='index'),
    re_path(r'^(?P<album_id>[0-9])/$', views.detail, name='detail'),
]

If it doesn’t work add this code to yoursite\urls.py inside urlpatterns:

path('music/<int:album_id>/', views.detail, name="detail"),

Use an empty string ” instead of ‘/’ or r’^$’. It works like a charm. Code is as below:

from django.urls import path, re_path

urlpatterns = [
    path('admin/', admin.site.urls),
    path('', home, name='home'),
]

In django 2.0 version primary key write this way…

urls.py

from django.urls import path

from . import views


urlpatterns = [
    path('', views.course_list),
    path('<int:pk>/', views.course_detail),
]