Setting browser/os restrictions on Django

I’m new to django programming, not python, and could do with a hand.

I am attempting to make a website exclusive to a certain device. I have created a disallow page accessible by ‘/disallow/’. How do I go about running os/browser checks that then redirect in the event the os/browser is not on the verified list.

I know the information I am wanting to check will be in the request and I can use

request.META['HTTP_USER_AGENT']

However where do I write any logic required and how could I apply this to any page the user tries to access.

Any help would really be appreciated Ed