Question

I was going through the django tutorial and though now almost everything there seems pretty clear, I am having trouble understanding the regex while matching the urls :

r'^(?P<poll_id>\d+)/$

what does (?P<poll_id>\d+) do ?

I am understanding that after stripping off the "34/" from "polls/34/", The polls.url is being called and there the keyword urlpatterns is being looked for , but how does poll_id get this value 34 ?

I know only a bit of regex, so thats why it might be hard for me to read.
Also, here is the reference that I am using for this question :Tutorial Part3

Answer 1

It’s a regex that takes the poll_id (a number) as a variable.

The corresponding view is:

def detail(request, poll_id):
    return HttpResponse("You're looking at poll %s." % poll_id)

Now when you go to example.com/polls/34/, it knows you are looking for poll number 34, and it brings that in to the view as the poll_id.

So in your view, poll_id = 34. This allows you to display or manipulate this specific poll.

Essentially the point of the regex in this case is to allow you to view a large number of specific polls without having to create an explicit url for each one.

To clarify, this regex is saying take any number \d+, save it as poll_id, and proceed to this view with that poll_id.