I'm incredibly new to Python and I hope I'm not asking a dumb question. I also hope I can explain this clearly.

1. I have two lists that each give user activity in one column, and userID in the other. The two lists correspond to consecutive time periods of two weeks. (list 1 = july1-14, list 2 = july15-30)

2. I want to isolate users from the 2nd list that have had NO activity prior to the beginning of the 2nd time period. In other words, for all user appears that appear in the first list, I want their data (userID and activity) eliminated from the 2nd list. This way, I isolate users that began and ended within the 2nd time period.

Any suggestions?