identical views different URLs - django

Question

I have following routs:
url(r'^future/programs/$', main.programs, {'period': 'future'}),
url(r'^past/programs/$', main.programs, {'period': 'past'}),
When I try to display link in template, using template tag url like this
{% url main.views.main.programs %}
I always get link /past/programs/. When I try like this
{% url main.views.main.programs period="future" %}
I get an error:
Caught NoReverseMatch while rendering: Reverse for
'main.views.main.programs' with arguments '()' and keyword arguments
'{'period': u'future'}' not found.
How i can display link to /future/programs/?

Answer 1

I think you might want to approach it with one single url pattern:
url(r'^(?P(<period>[\w]+)/programs/$', main.views.programs),
and in your view:
def programs(request, period):
if period == 'future':
...
elif period == 'past':
...
and in templates:
{% url main.views.main.programs period="future" %}
In your approach, you are mistaking the forward flow with the reverse flow, i.e. the extra keyword arguments of the url conf with the keyword arguments that are passed to match a pattern.
The former is extra data you are allowed to pass to a view when it is matched (i.e. when a user goes to /future/programs/, the pattern is matched and period=future is passed to the view), the latter is the actual data used to match the url (i.e. the period=future is passed to the reverse() function which tries to match a pattern that excepts those keyword arguments - which you haven't outlined)
Edit:
A more appropriate pattern to use in your url would be something like:
url(r'^(?P(<period>past|future)/programs/$', main.views.programs),
where the selection could only be 'past' or 'future'. This is fine for incoming urls, but django's reverse() function (which is used in the url template tag) can't handle alternative choices:
https://docs.djangoproject.com/en/dev/topics/http/urls/#reverse
The main restriction at the moment is that the pattern cannot contain alternative choices using the vertical bar ("|") character.

Answer 2

I would rather assign each url a name:
url(r'^future/programs/$', main.programs,
{'period': 'future'},
name='future_programs'),
url(r'^past/programs/$', main.programs,
{'period': 'past'},
name='past_programs'),
And to display the link in your template:
Past programs: {% url past_programs %}
Future programs: {% url future_programs %}
I think this solution is better because if you just have two options for that view, you can forget about passing parameters and validating them.
Now, if those two options (future, past) can grow into several more, the other solution would be better, but I think this is not the case.