old_contents: from django.conf.urls import url
  from . import views
  
  urlpatterns = [
      url(r'^$', views.posts_home),
      url(r'^create/', views.post_create),
      url(r'^index/', views.post_list),
  ]
new_contents: from django.conf.urls import url
  from . import views
  
  urlpatterns = [
      url(r'^$', views.posts_home),
      url(r'^index/', views.post_list, name = 'index'),
      url(r'^create/', views.post_create, name = 'create'),
      url(r'^edit/(?P<id>\d+)/$', views.post_edit, name = 'edit'),
  ]
subject: add url edit