django how to pass parameter from url to view

Question

I'm trying to append a parameter no_rep at the end of my question url as a signal to show different views. I'm using Django 1.8 and following the url pattern from askbot.

This is the url.py :

url(
        (r'^%s(?P<id>\d+)/' % QUESTION_PAGE_BASE_URL.strip('/') +
        r'(%s)?' % r'/no-rep:(?P<no_rep>\w+)'),
        views.readers.question,
        name='question'
    ),

I'm trying to show different displays depending on the value of no_rep in my url.

This is the view :

def question(request, id, no_rep):
    if no_rep == '1':
        request.session['no_rep'] = True
    else:
        request.session['no_rep'] = False

I couldn't find information on what the +,%,? do, which is probably where the problem is. Could someone explain how the regex work with the base url? When I enter the url http://localhost:8000/question6/test-question/no_rep:1 , request.session['no_rep'] should be set to true, but it's not. What am I missing?

Answer 1

Your url looks like this after all substitutions (%): r'^question(?P<id>\\d+)/(/no-rep:(?P<no_rep>\\w+))?' , so:
1. Missing part for test-question
2. You have odd grouping around named group no_rep (which is legal, but not recommended )

So for url like http://localhost:8000/question6/test-question/no_rep:1 your url pattern should look like this:
r'^%s(?P<id>\\d+)/test-question/(?:no_rep:(?P<no_rep>\\d+))?' % QUESTION_PAGE_BASE_URL.strip('/') r'^%s(?P<id>\\d+)/test-question/(?:no_rep:(?P<no_rep>\\d+))?' % QUESTION_PAGE_BASE_URL.strip('/') (you can change \\d+ in the last group for \\w+ if you want letters to match too).

About non-capturing groups (?:...) and meaning of + and ? you can read in the documentation of Python re module.

Answer 2

Change your url patterns to something like this,

urlpatterns = [
                  url(r'question/(?P<id>\d+)/no-rep/(?P<no_rep>\w+)/', question),

              ]

OR

QUESTION_PAGE_BASE_URL = "question"
urlpatterns = [
                  url(r'{QUESTION_PAGE_BASE_URL}/(?P<id>\d+)/no-rep/(?P<no_rep>\w+)/'.format(
                      QUESTION_PAGE_BASE_URL=QUESTION_PAGE_BASE_URL), question),

              ] + router.urls

NOTE :
It's not good idea to use named groups like id along with some string or char like urls, ( localhost:8000/question6/ )