Optional get parameters in django?

Question

Can someone please explain how you can write a url pattern and view that allows optional parameters? I've done this successfully, but I always break the url template tag.

Here's what I have currently:

Pattern

(r'^so/(?P<required>\d+)/?(?P<optional>(.*))/?$', 'myapp.so')

View

def so(request, required, optional):

If I use the url template tag in this example providing both arguments, it works just fine; however, if I omit the optional argument, I get a reversing error.

How can I accomplish this?

Thanks, Pete

Answer 1

I generally make two patterns with a named url:

url(r'^so/(?P<required>\d+)/$', 'myapp.so', name='something'),
url(r'^so/(?P<required>\d+)/(?P<optional>.*)/$', 'myapp.so', name='something_else'),

Answer 2

Why not have two patterns:

(r'^so/(?P<required>\d+)/(?P<optional>.*)/$', view='myapp.so', name='optional'),
(r'^so/(?P<required>\d+)/$', view='myapp.so', kwargs={'optional':None}, name='required'),

Answer 3

Others have demonstrated the way to handle this with two separate named URL patterns. If the repetition of part of the URL pattern bothers you, it's possible to get rid of it by using include():

url(r'^so/(?P<required>\d+)/', include('myapp.required_urls'))

And then add a required_urls.py file with:

url(r'^$', 'myapp.so', name='something')
url(r'^(?P<optional>.+)/$', 'myapp.so', name='something_else')

Normally I wouldn't consider this worth it unless there's a common prefix for quite a number of URLs (certainly more than two).