python - Designing a Django voting system without using accounts -

we considering implementing voting system (up, down votes) without using type of credentials--no app accounts nor openid or of sort.

concerns in order:

1. prevent robot votes
2. allow individuals under nat vote without overriding/invalidating else's vote
3. preventing (or, @ least making difficult for) users vote more once

my questions:

1. if you've implemented similar, tips?
2. any concerns perhaps i'm overlooking?
3. any tools should perhaps into?

if have questions in forming answer of these questions, please ask in comments!

to address concerns:

1: simple captcha trick, if google "django captcha", there bunch of plugins. i've never used them myself, can't best.

2 & 3: using django's sessions addresses both of these problems - save cookie on user's browser indicate person has voted. allows people vote via different browsers or clearing cache, depends on how important people not allowed vote twice. imagine small percentage of people think try clearing cache, though. far know other way limit users without sign-in process test ip addresses, violate second criteria since people on same network show having same ip address.

if don't want multiple votes simple deleting browser cookies, allow facebook or twitter login - django-socialregistration plugin pretty documented , straightforward implement.

hope helps!