Is there anything that pickle + copy_reg cannot serialize?

[Maurice LING]

Hi,

I need to look into serialization for python objects, including codes, 
recursive types etc etc. Currently, I have no idea exactly what needs to 
be serialized, so my scope is to be as wide as possible.

I understand that marshal is extended by pickle to serialize class 
instances, shared elements, and recursive data structures 
(http://www.effbot.org/librarybook/pickle.htm) but cannot handle code 
types. pickle can be used together with copy_reg and marshal to 
serialize code types as well 
(http://www.effbot.org/librarybook/copy-reg.htm).

So my question will be, are there anything that pickle/copy_reg/marshal 
combination cannot serialize? If so, what are the workarounds?

Thanks
Maurice