serialization and versioning

[Neal Becker]

I wonder if there is a recommended approach to handle this issue.

Suppose objects of a class C are serialized using python standard pickling.  
Later, suppose class C is changed, perhaps by adding a data member and a new 
constructor argument.

It would see the pickling protocol does not directly provide for this - but is 
there a recommended method?

I could imagine that a class could include a class __version__ property that 
might be useful - although I would further expect that it would not have been 
defined in the original version of class C (but only as an afterthought when it 
became necessary).