big objects and avoiding deepcopy?

[Terry Reedy]

bearophileHUGS at lycos.com wrote:
> Robert Kern:
>> This is similar to implementing "Undo" functionality in applications.<
> 
> In a quite-high-level language (like Python, but not necessarily in
> Python itself) it may become eventually advantageous to add some (even
> limited) built-in form of undo.

Right now, I believe, one could develop an undo module with undolist and 
undodict classes that wrap instance mutations with an append to an 
undoinfo list.