pickle/zodb: how to handle moving .py files with class definitions?
Unfortunately, there is no easy solution. You can convert your old-style objects with the refactored ones (I mean classes which are in another file/module) by the following schema

add the refactored classes to your code without removing the old-ones
walk through your DB starting from the root and replacing all old objects with new equivalents
compress your database (that's important)
now you can remove your old classes from the sources
I'm using ZODB which, as I understand it, uses pickle to store class instances. I'm doing a bit of refactoring where I want to split my models.py file into several files. However, if I do this, I don't think pickle will be able to find the class definitions, and thus won't be able to load the objects that I already have stored in the database. What's the best way to handle this problem?