Heroku: how to store a variable that mutates?
Have to agree with @KlausD, doing what you are suggesting is actually a bit more complex trying to work with a filesystem that won't change and tracking state information (last selected) that you may need to persist. Even if you were able to store the last item in some environmental variable, a restart of the server would lose that information.
Adding a db, and connecting it to python would literally take minutes on Heroku. There are plenty of well documented libraries and ORMs available to create a simple model for you to store your list and your cursor. I normally recommend against storing pointers to information in preference to making the correct item obvious due to the architecture, but that may not be possible in your case.
I have deployed a small application to Heroku. The slug contains, among other things, a list in a textfile. I've set a scheduled job to, once an hour, run a python script that select an item from that list, and does something with that item.
The trouble is that I don't want to select the same item twice in sequence. So I need to be able to store the last-selected item somewhere. It turns out that Heroku apparently has a read-only filesystem, so I can't save this information to a temporary or permanent file.
How can I solve this problem? Can I use os.environ in python to set a configuration variable that stores the last-selected element from the list?