How to implement a 'Vote up' System for posts in my blog?
If voting is only for subscribed users, then enable voting after members log in to your site. 
If not, then you can track users' IP addresses so one IP address can vote once for a single article in a day.
By the way, what kind of security do you need?
I have written a simple blog using Python in google app engine. I want to implement a voting system for each of my posts. My posts are stored in a SQL database and I have a column for no of votes received. Can somebody help me set up voting buttons for individual posts? I am using Jinja2 as the templating engine. 
How can I make the voting secure? I was thinking of sending a POST/GET when someone clicks on the vote button which my python script will then read and update the database accordingly. But then I realized that this was insecure. All suggestions are welcome.