pyramid-tutorial | Create a Pyramid app from scratch | Learning library

This is a different HTTPNotFound exception and it is raised at the route-matching step before your view is even executed. The reason is that you have config.add_route('view', '/{id}'). Note the /{id} NOT /{id}/. Pyramid considers these two different routes and thus the latter does not match. The simplest solution to this is to register all of our canonical routes with a / suffix such as /{id}/ and then pass append_slash=True to your notfound view configuration such as config.add_notfound_view(..., append_slash=True) or @notfound_view_config(append_slash=True). This will trigger a redirect when a user visits the version without the trailing slash.