Using variables in Django urlpatterns

Question

The components of the URLs of the Django app I'm working on are very 'pluggable', and different combinations of them get used in various urlpatterns, so our urls.py looks something like:

rev = r'(/R\.(?P<rev>\d+))?'
repo_type= r'^(?P<repo_type>svn|hg)/'
path = r'/dir/(?P<path>.*)$'
# etc.

urlpatterns = patterns('',
    (repo_type_param + r'view-source' + opt_rev_param + path_param, view_source),
    (repo_type_param + r'history' + path_param, history),
    (repo_type_param + r'revision' + opt_rev_param + r'/$', revision),
) #etc.

Which seems like a nice way to keep things clean. However, I found I kept getting NoReverseMatch errors when I tried to reverse any of the views pointed to by the urlpatterns. After a lot of tinkering, I found that using the full raw string in the pattern, rather than concatenating the substrings, fixed the problem.

So, is it really necessary to use only raw strings in urlpatterns? I couldn't find this documented anywhere. Bug or feature? Having to copy and paste regex patterns that get used repeatedly seems like a violation of DRY.

One of the things python likes to follow is being explicit over implicit - this might be a possible reason for not allowing the concatenation. Although I would be very surprised if there is not a way to do what you are after. :-) — REA_ANDREW
– REA_ANDREW, Commented Jul 4, 2010 at 8:42

Joseph Spiros · Accepted Answer · 2012-05-20 09:48:44Z

1

I'm not sure about concatenation, but I know you can format raw strings and use them in urlpatterns. See BlogView.urlpatterns for an example.

edited May 20, 2012 at 9:48

answered Jul 6, 2010 at 5:59

Joseph Spiros

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ebt · Accepted Answer · 2010-07-04 09:11:05Z

1

I found that this pattern works for redirects and might help in your case (unless I am interpreting your question incorrectly). I couldn't reverse a pattern within the same tuple but if I defined a new tuple and then concatenated a new tuple to the original Djanogo would reflect without issue. ex:

  urlpatterns = patterns('',
         ('^foo/$','foo.views.foo')
  )
  urlpatterns+= patterns('',('^$','django.views.generic.simple.redirect_to',{'url':reverse('foo.views.foo')}))

answered Jul 4, 2010 at 9:11

ebt

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will.i.am · Accepted Answer · 2010-07-04 15:56:36Z

0

You can use a name to identify your url pattern like this:

urlpatterns = patterns('',
     url(repo_type_param + r'view-source' + opt_rev_param + path_param, view_source, name='myurlname'),
)

Note the url and name, and then reverse match like this:

reverse('myurlname', kwargs={'groupname': 'value'})

Hope it helps

answered Jul 4, 2010 at 15:56

will.i.am

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