Home Original page

[Python-Dev] backwards and forwards compatibility, the exact contents of pickle files, and IntEnum

Antoine Pitrou solipsis at pitrou.net
Sun Mar 15 16:10:51 CET 2015 
On Sat, 14 Mar 2015 22:52:17 -0700
Ethan Furman <ethan at stoneleaf.us> wrote:

> I'm not sure exactly how to phrase this inquiry, so please bear with me.
> 
> What exactly does backwards compatibility mean as far as pickle goes?  We have the various protocols, we have the
> contents of pickle files created at those protocols, and we have different versions of Python.
> 
> Should a pickle file created in Python 3.4 with protocol 3 and the contents of socket.AF_INET be unpicklable with a
> Python 3.3 system?  Because currently it cannot be as socket.AF_INET became an IntEnum in 3.4.
> 
> I'm thinking the answer is yes, it should be.

I agree with you that this should not break.

> So, the final question:  Do the contents of a pickle file at a certain protocol have to be the some between versions, or
> is it enough if unpickling them returns the correct object?

It's certainly enough if unpickling returns the correct object. Exact
serialization is an implementation detail.

Regards

Antoine.
More information about the Python-Dev mailing list