Object Diffs

[Steven D'Aprano]

Croepha wrote:

> Hello Python list:
> 
> I am doing research into doing network based propagation of python
> objects.  In order to maintain network efficiency. I wan't to just
> send the differences of python objects,

Can you explain in more detail what you mean?

Are there constraints on what the objects can be? If you have two objects:

a = None
b = (1, 2, "hello world", [])

how would you describe the diff between a and b?

If a and b are both numbers, the diff between them is just a-b, but this
itself is a number and so transmitting it takes exactly as much memory as
just sending b.

Obviously if a and b are strings, the problem becomes trivial (just
transmitted the string diff, which is a solved problem).

> I was wondering if there 
> was/is any other research or development in this area? I was thinking
> that I could look at how pickle works an implement a diff system
> there, or I could actually create a pickle of the object and then use
> difflib to compare the flattened text...

The source code for pickle is available. See the pickle.py and
pickletools.py files in your Python installation.

Also, these resources may help:

http://wiki.python.org/moin/DistributedProgramming
http://wiki.python.org/moin/ParallelProcessing


-- 
Steven