[Zope3-Users] What attributes are made persistent

[Peter Bengtsson]

On 2/16/06, Jeff Shell <eucci.group at gmail.com> wrote:
> One could, but it's really not worth it. It's just the laws of Python
> and mutability and immutability :). (It took me years to understand
> those terms. I kept associating them with 'mutable' in the "can be
> made quiet" sense... Eventually my music brain stepped back and I went
> "oh, MUTATE! Ahhh!". Seriously, it took me about four years to
> understand that :).
>
Wow! I think I love you Jeff. Not only do you reply with
non-condencending constructive advise you also confess to [past]
weaknesses.

>
> Personally, I seldom store lists, or even use them as attributes on
> instances. Even outside of Zope/ZODB, I've found myself accidentally
> losing data because I was carelessly using the reference. Tuples for
> everybody!
>

Ok. Sounds sensible.
I've learnt something: use BTrees() instead of dict(), use tuple()
instead of list().


> On 2/15/06, Shaun Cutts <shaun at cuttshome.net> wrote:
> > Well, one could have a base class along the lines of
> >
> > class PersistSetItemOnAttributes:
> >
> >     def __setattr__( self, attr, val ):
> >         oldSI = val.__class__.__dict__.get( '__setitem__', None )
> >         if oldSI is not None:
> >             def newSI( vself, vattr, vval ):
> >                 vself._p_changed = True     # is this the right member?
> >                 oldSI( vattr, vval )        # oldSI is bound: no vself?
> >             val.__class__.__setitem__ = newSI
> >         super( PersistSetItemOnAttributes, self ).__setattr__( attr, val
> > )
> >
> > Of course, this is really just pseudocode. For one thing, need to trap
> > whether 'val' is really a class. For another if you were serious about
> > this, you would want to check if the obj wasn't persistent first, and
> > you might want to do it recursively. And while your are at it, you might
> > want to check on other mutators as well....(for instance, check first
> > what sequence interface if any 'val' supports...)
> >
> > ... sounds like too much work, and would be problem prone even so. After
> > all, some things you don't want to be persistent!
> >
> > - Shaun
> >
> > > -----Original Message-----
> > > From: zope3-users-bounces at zope.org
> > [mailto:zope3-users-bounces at zope.org]
> > > On Behalf Of Stephan Richter
> > > Sent: Wednesday, February 15, 2006 8:43 AM
> > > To: zope3-users at zope.org
> > > Cc: Florian Lindner
> > > Subject: Re: [Zope3-Users] What attributes are made persistent
> > >
> > > On Wednesday 15 February 2006 08:21, Peter Bengtsson wrote:
> > > > class PersistentAnything(PersistentMapping, PersistentList,
> > > > PersistentDict):
> > >
> > > AAhhhh! This is so wrong! It merges two incompatible APIs: collections
> > and
> > > mappings. The non-persistent equivalent to this is:
> > >
> > >   >>> class DoEverything(set, list, dict):
> > >   ...  pass
> > >
> > > > Am I just trying to make it too simple?
> > >
> > > I think you try far too hard to not understand why the persistent
> > > mechanism
> > > works as it does. You make your life harder than it has to be.
> > >
> > > Regards,
> > > Stephan
> > > --
> > > Stephan Richter
> > > CBU Physics & Chemistry (B.S.) / Tufts Physics (Ph.D. student)
> > > Web2k - Web Software Design, Development and Training
> > > _______________________________________________
> > > Zope3-users mailing list
> > > Zope3-users at zope.org
> > > http://mail.zope.org/mailman/listinfo/zope3-users
> >
> >
> >
> > _______________________________________________
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> > Zope3-users at zope.org
> > http://mail.zope.org/mailman/listinfo/zope3-users
> >
>
>
> --
> Jeff Shell
> _______________________________________________
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> Zope3-users at zope.org
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>


--
Peter Bengtsson,
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