How to integrate Python script with Splunk (input, output)

I have a Splunk alert which returns some JSON results as well as the usual Splunk fields and sends them by email to several recipients. The results are not so readable by humans, so I have created a Python script to beautify them so they keep only the strictly necessary information and present it to the users in a neat way. I know that I can pass a Python script in an alert configuration, however I'm not sure how the Python script can get the input values (the JSONs from the alert) nor what format to use for the output so it replaces the old JSONs in the emails. My script calculates a priority score for each JSON in the email and I was wondering whether there was a way to include the highest score value in the subject of the email (I read about the variables, but couldn't find anything useful)... Please advise.