[Python-Dev] The memo of pickle

[Guido van Rossum]

> > Perhaps pickle could grow an option to assume that a
> > data structure is non-recursive ?
> 
> Then you'd probably want some means of detecting cycles, or you'd get
> infinite recursion when you got it wrong. That would mean keeping a
> stack of objects, I think -- probably less memory than keeping all of
> them at once.

cPickle has an obscure options for this.  You create a pickler object
and set the attribute "fast" to True, I believe.  It detects cycles by
using a nesting counter, I believe (read the source to learn more).

> But I think the idea of keeping the object references in a list is
> well worth trying first. 4 bytes per object instead of 36 sounds like a
> good improvement to me!

So maybe we need to create an identitydict...

--Guido van Rossum (home page: http://www.python.org/~guido/)