expanding persistant objects

[Pete Shinners]

i'm learning python here and have a question about storing
persistant objects. i plan to keep a real simple list of
users and i want to know the best way to simple store it
and reload it.
my only concern is that later i'll probably want to add
more fields to each users record. can simple pickling
handle this? do i need to use one of the DB storage
libraries?

i'm worried if i start saving the data one way, when i go
to add extra fields i wont be able to load the files anymore.

thanks for any guidance!