[Python-Dev] Pickler/Unpickler API clarification

[Guido van Rossum]

On Sat, Mar 7, 2009 at 8:04 AM, Michael Haggerty <mhagger at alum.mit.edu> wrote:
> Typically, the purpose of a database is to persist data across program
> runs.  So typically, your suggestion would only help if there were a way
> to persist the primed Pickler across runs.

I haven't followed all this, but isn't is at least possible to
conceive of the primed pickler as being recreated from scratch from
constant data each run?

> (The primed Unpickler is not quite so important because it can be primed
> by reading a pickle of the primer, which in turn can be stored somewhere
> in the DB.)
>
> In the particular case of cvs2svn, each of our databases is in fact
> written in a single pass, and then in later passes only read, not
> written.  So I suppose we could do entirely without pickleable Picklers,
> if they were copyable within a single program run.  But that constraint
> would make the feature even less general.

Being copyable is mostly equivalent to being picklable, but it's
probably somewhat weaker because it's easier to define it as a pointer
copy for some types that aren't easily picklable.

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