[Python-Dev] PyPy, Jython, & IronPython: Enum convenience function and pickleablity

[Antoine Pitrou]

On Thu, 2 May 2013 13:33:21 -0700
Eli Bendersky <eliben at gmail.com> wrote:

> On Thu, May 2, 2013 at 1:22 PM, Antoine Pitrou <solipsis at pitrou.net> wrote:
> 
> > On Thu, 2 May 2013 13:15:00 -0700
> > Eli Bendersky <eliben at gmail.com> wrote:
> > > > Two things that were suggested in private:
> > > >
> > > > 1) ask users to pass the module name to the convenience function
> > > > explicitly (i.e. pass "seasonmodule.Season" instead of "Season" as the
> > > > class "name"). Guido doesn't like it :-)
> > > >
> > > > 2) dicth the "convenience function" and replace it with a regular
> > > > class-based syntax. Ethan doesn't like it :-)
> > > >
> > >
> > > Re (2), we already have the hack in stdlib in namedtuple, so not allowing
> > > it for an enum is a step backwards.
> >
> > That's a fallacy. There is no step backwards if you adopt a class-based
> > syntax, which is just as convenient as the proposed "convenience
> > function". I have a hard time understanding that calling a function to
> > declare a class is suddenly considered "convenient".
> >
> > > If
> > > sys._getframe(1).f_globals['__name__'] feels hackish, maybe it can be
> > > shortened to a convenience function the stdlib provides?
> >
> > It's not the notation which is hackish, it's the fact that you are
> > inspecting the frame stack in the hope of getting the right information.
> >
> > What if someone wants to write another convenience function that wraps
> > your convenience function? What if your code is executing from some
> > kind of step-by-step debugger which inserts an additional frame in the
> > call stack? What if someone wants the enum to be nested inside another
> > class (rather than reside at the module top-level)?
> >
> 
> Would nesting the non-convenience Enum in a function or a class allow one
> to pickle it?

Once PEP 3154 is implemented (Alexandre is on it :-)), nested classes
should be picklable. As for classes inside functions, it sounds quite
impossible (how do you instantiate the function namespace without
calling the function?).

Regards

Antoine.