Best practice for running a daily Python screen-scraping script 50 times (8.3 minutes total) per user?
Assuming you're using a database to store the users' web sites, you can have just 1 script that runs as a daily cron job and queries the database for the list of sites to process.
On the front-end, I have a PHP webapp that allows users to create a list of their websites (5 max).
On the back-end, a Python script runs daily (and has ~10 iterations) for each website that the user registers. Each script per website takes about 10 seconds to run through all iterations and finish its scraping. It then makes a CSV file with its findings.
So, in total, that's up to (5 websites * 10 iterations =) 50 iterations at 8.3 total minutes per user.
Right now, the script works when I manually feed it a URL, so I'm wondering how to make it dynamically part of the webapp.

How do I programmatically add and remove scripts that run daily depending on the number of users and the websites each user has each day?
How would I schedule this script to run for each website of each user, passing in the appropriate parameters?

I'm somewhat acquainted with cronjobs, as it's the only thing I know of that is made for routine processes.