Django guests vote only once poll
If it is that important that people can only vote once, consider creating a basic registration / login system anyway. A guest can always use multiple computers to skew the voting while account registration at least allows you to track which e-mail addresses are being used to vote. It also takes a bit more effort to skew the voting that way. If it's important but not of life-saving importance then I would use the cookie approach for anonymous guests.
I'm new to Django but am working on the tutorial on the Django website for creating a poll.
What is the best way to make it so guests (no registration / login) can only vote once on a poll?

IP (Don't want IP because people sharing a network can only vote once).
Cookie (User can delete the cookie but seems like the best approach).
Session (If the user closes the browser the session will change).

I'm guessing that Cookie would be the best approach but is there a better way for Django?