[Python-ideas] new pickle semantics/API

Josiah Carlson jcarlson at uci.edu
Fri Jan 26 01:14:42 CET 2007

"Collin Winter" <collinw at gmail.com> wrote:
> On 1/25/07, Josiah Carlson <jcarlson at uci.edu> wrote:
> > "tomer filiba" <tomerfiliba at gmail.com> wrote:
> > > repr is made for humans of course, while serialization is
> > > made for machines. they serves different purposes,
> > > so they need different APIs.
> >
> > I happen to disagree.  The only reason to use a different representation
> > or API is if there are size and/or performance benefits to offering a
> > machine readable vs. human readable format.
> [snip]
> > I'm know that there are real performance advantages to using (c)Pickle
> > over repr/unrepr, but I use it also so that I can change settings with
> > notepad (as has been necessary on occasion).
> [snip]
> > > all i'm after is the state of the object (which is expressed in terms of
> > > other, more primitive objects).
> >
> > Right, but as 'primative objects' go, you cant get significantly more
> > primitive than producing a string that can be naively understood by
> > someone familliar with Python *and* the built-in Python parser.
> > Nevermind that it works *today* with all of the types you specified
> > earlier (with the exception of file objects - which you discover on
> > parsing/reproducing the object).
> You use pickle because it's more general than repr/unrepr, not because
> it's faster or the result is smaller. Assuming you're talking about
> the ConfigObj's unrepr mode
> (http://www.voidspace.org.uk/python/configobj.html#unrepr-mode),

*I* use pickle when I want speed.  I use repr and unrepr (from configobj)
when I want to be able to change things by hand.  None of the objects I
transfer between processes/disk/whatever are ever more than base Python

As for whatever *others* do, I don't know, I haven't done a survey. 
They may do as you say.

> Pickle -- and the simplification API Tomer is proposing -- is far more
> general than that. repr/unrepr is in no way a substitute.

I never claimed it was a substitute, I stated quite clearly up front;
"My only criticism will then be the strawman repr/unrepr."  The
alternate strawman is repr/eval, can be made to support basically
everything except for self-referential objects.  It still has that
horrible security issue, but that also exists in pickle, and could still
exist in the simplification/rebuilding rutines specified by Tomer.

 - Josiah

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