Keep a script running in the background

[Guillermo]

These are the basic requirements:

Script A must keep a dictionary in memory constantly and script B must
be able to access and update this dictionary at any time. Script B
will start and end several times, but script A would ideally keep
running until it's explicitly shut down.

I have the feeling the way to do this is Python is by pickling the
dict, but I need the method that gives the best performance. That's
why I'd rather want to keep it in memory, since I understand pickling
involves reading from and writing to disk.

I'm using SQLite as a database. But this dict is an especial index
that must be accessed at the highest speed possible.