Timer object in Django
You should not use some in-process/memory timer objects since your django app can run in multiple processes...
I suggest create this "timers" in database (like "expire" datetime field for your product model) and use cron job that will mark expired objects to be available
I'm using Django to create registration/payment application for a limited number of products.    I want to create a timer so that when a user chooses to purchase a product, that product will then displayed as "already taken".  But, if the user the user does not go through with the purchase and the timer runs out, the product goes back to status "available".  If the user completes the purchase, the timer should cancel, leaving the product's status permanently as "already taken".  
I've tried using python's dictionary to instantiate python Timer objects of the fly, but about 30% of the time, I get a "key error" when it's time to cancel the Timer.  
Please.  Could someone give me an idea on the proper way to do this in Django?
Thanks very much!
Mark