[Python-3000] Is pickle's persistent_id worth keeping?

Phillip J. Eby pje at telecommunity.com
Sun Jan 6 04:58:10 CET 2008

At 06:50 PM 1/5/2008 -0500, Alexandre Vassalotti wrote:
>I currently trying to clean up the interface of the pickle module for
>Python 3K. So far, I haven't done much, except documenting parts the
>pickle stream format.
>There's still one thing I still don't understand about pickle,
>persistent_id. I haven't found any useful use-cases for it.

Any system that wants to be able to pickle parts of an object graph 
while retaining references.  Any system that wants to be able to 
handle missing, moved, or renamed classes when unpickling.

>  Using
>Google's code search, only Zope (or variant of) seems to have found
>some obscure way to use it.

Is Chandler considered a Zope variant now, and if so, why?  :)

>So, would it be okay to remove it from the next version of the protocol?

Chandler's .chex (Chandler export) files use this to handle class 
moves, or data for a missing or broken plugin.  If/when we'll ever 
use Python 3 is an open question, but if we did, we'd certainly 
continue to need it.

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