Re: Pickling errors with tz.FixedOffsetTimezone

On Sat, 2009-01-17 at 12:13 +0100, Lawrence Oluyede wrote:
> On Sat, Jan 17, 2009 at 11:51 AM, Federico Di Gregorio <fog-NGVKUo/i/[email protected]> wrote:
> > Il giorno ven, 16/01/2009 alle 13.22 +0100, Lawrence Oluyede ha scritto:
> >> I have a web application that uses memcached to store some data.
> >> Some of that data is retrieved through psycopg2 (2.0.8) and contains
> >> datetime instances.
> >>
> >> Sometimes I get the following exception while trying to put objects
> >> into the memcached cache:
> >> "PicklingError: Can't pickle <class
> >> 'psycopg2.tz.FixedOffsetTimezone'>: it's not the same object as
> >> psycopg2.tz.FixedOffsetTimezone"
> >
> > Once I was bitten by a very similar error. The module was loaded two
> > times from different paths and instances created with the first copy of
> > the module could not be pickled by the code that had the second copy
> > available. I didn't dig too much to understand what was happening
> > because we were in a hurry and simply making sure the was a single copy
> > of the module solved the problem.
> 
> Thanks, I'll try to do an in depth check of the program. Maybe there's
> some dependence that I'm not seeing in the surface triggering this
> kind of bad behavior. It's odd though.
> 

That happened to me too sometimes, importing a module once with a
complete packages path and somewhere into a sibling module using only
the module name. The result was having distinct foo.bar.MyClass and
bar.MyClass, and the isinstance test failing here and there.

You may try:

    for n, m in sys.modules.iteritems():
        c =  getattr(m, 'FixedOffsetTimezone', None) 
        if c: print n, id(c)

If somewhere the class has a different id, it may have been imported in
a strange way.

Bye!


-- Daniele