title: How to date-stamp a pickled object
body: <p>I have a script that obtains certain information online and stores it in a list.  I'd like to keep the list for future executions of the script, and then retrieve the information online again after a certain period of time (let's say 3 days), just in case it's gone stale.  My understanding is that I can pickle the list (but please let me know if there's a more advisable way to store it -- EDIT: should I use shelve or json instead?).</p>
  
  <p>My main question is this: what's the best and most idiomatic way to store the date and time of the pickle and then evaluate if 3 days have passed?</p>