[Answered ]-Django url pattern for DetailView

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Since this has not really been answered, yet:

  1. Is there any value in using double underscore in url pattern?

DRY, more or less:

class SomeDetailView(...):
     def get_queryset(self):
         queryset = super(SomeDetailView, self).get_queryset()
         # grab all named URL keyword arguments and 
         # transform them into field lookup patterns.
         # Leave out slug and primary key keywords, though.
         filter_args = {
              k: v for k, v in self.kwargs.iteritems()
              if k not in (self.slug_url_kwarg, self.pk_url_kwarg)
         }
         if filter_args:
             queryset = queryset.filter(**filter_args)
         return queryset

Since e.g. pub_date__year is a valid field lookup you –possible security problems nonwithstanding– just gained the ability to add lookup criteria solely via named capture patterns in urls.py.

  1. When I reduce the url pattern to the following, I only get a 404 when requesting the page with: 127.0.0.1:8000/test/ (test is the slug for an existing record stored in db)
url(r'^/(?P<slug>[a-zA-Z0-9-]+)/?$', DetailView.as_view(model=Post, )),   
       ^ leading slash

That’s common enough mistake that it made it into documentation:

There’s no need to add a leading slash, because every URL has that. For example, it’s ^articles, not ^/articles.

Try again with r'^(?P<slug>[a-zA-Z0-9-]+)/?$'

Documentation is, however, a little misleading, here. “There’s no need” should be read as “The initial leading slash is matched automatically and is not part of the url pattern“.

👤dhke

1👍

Those ?Ps are just capturing patterns in a regex; they are names and can be whatever you want, but will be passed as keyword arguments. They need a <name> (ex (?P<name>) ) or they will be passed as regular arguments, which is why your reduced example failed.

Personally I reserve __s for db lookups, and would use something like (?<pub_year>) as a more descriptive variable name.

There are default conventions in class-based-views that let you use standard names to write really terse code. In DetailView, ‘slug’ is the default slug_field and slug_url_kwarg; if you trace the dispatch() pattern through, you will see where those defaults can be tweaked/how they are used. BTW: CCBV is really useful and you should use it, and your tutorial link appears broken.

👤bwarren2

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