Re: [Zope-dev] zope.xmlpickle

26 May 2006


      Michael Dunstan wrote:
...
Hi all,
I have been trying out ``zope.xmlpickle`` as a alternative to
XMLExportImport in Zope2.
Cool. xmlpickle is really a newer version of the xml pickler used in
Zope 2's export/import.  It's main goal is to provide nicer pickles:

- More readable

- More diff friendly.  It does this my:

   - sorting dictionary items

   - eliminating unused memo references

It would be nice to integrate this back into the export/import
machinery.  Some care would be needed to make it compatible with
the old xml pickles.
...
Seems to do the job just fine. Grab Zope
2.9.3 and install zope.xmlpickle by hand using something of the form:
% cd /opt/Zope-2.9/lib/python/zope
 % svn checkout 
svn://svn.zope.org/repos/main/Zope3/trunk/src/zope/xmlpickle
Then using zopectl debug:
...
...
...
from zope.xmlpickle import dumps
Picking on something simple to start with:
...
...
...
xml = dumps(app.acl_users.aq_base)
print xml
 <?xml version="1.0" encoding="utf-8" ?>
 <pickle>
   <initialized_object>
     <klass>
       <global name="__newobj__" module="copy_reg"/>
     </klass>
     <arguments>
       <tuple>
         <global name="SiteErrorLog"
module="Products.SiteErrorLog.SiteErrorLog"/>
       </tuple>
     </arguments>
     <state>
       <dictionary>
         <item key="_ignored_exceptions">
             <tuple>
               <string>Unauthorized</string>
               <string>Redirect</string>
               <string>NotFound</string>
             </tuple>
         </item>
         <item key="copy_to_zlog">
             <true/>
         </item>
         <item key="keep_entries">
             <int>20</int>
         </item>
       </dictionary>
     </state>
   </initialized_object>
 </pickle>
That looks okay. But I strike problems with ``Missing.Value`` when
trying this on something that includes a catalog. The simplest way
to recreate the problem::
...
...
...
import Missing
dumps(Missing.Value())
 Traceback (most recent call last):
   File "<stdin>", line 1, in ?
   File "/opt/Zope-2.9/lib/python/zope/xmlpickle/xmlpickle.py", line
146, in dumps
     p = _dumpsUsing_PicklerThatSortsDictItems(ob, 1)
   File "/opt/Zope-2.9/lib/python/zope/xmlpickle/xmlpickle.py", line
73, in _dumpsUsing_PicklerThatSortsDictItems
     _PicklerThatSortsDictItems(file, bin).dump(object)
   File 
"/Library/Frameworks/Python.framework/Versions/2.4/lib/python2.4/pickle.py",
line 231, in dump
     self.save(obj)
   File 
"/Library/Frameworks/Python.framework/Versions/2.4/lib/python2.4/pickle.py",
line 324, in save
     self.save_global(obj, rv)
   File 
"/Library/Frameworks/Python.framework/Versions/2.4/lib/python2.4/pickle.py",
line 753, in save_global
     module = whichmodule(obj, name)
   File 
"/Library/Frameworks/Python.framework/Versions/2.4/lib/python2.4/pickle.py",
line 825, in whichmodule
     if func in classmap:
 TypeError: unhashable type
Meanwhile, dumps seems to work quite happy with many other examples
that I tried. Including all the content of a plone site minus a couple
of the catalogs. And ``zope.xmlpickle.loads`` seems to do the right 
thing too.
Any suggestions on getting a successful dumps of a Missing.Value?
You need someone with pickle zen to look at this.  I don't have time
right now myself.  If you don't find any other takers, then put an
issue in the Zope 3 collector.

Jim

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Jim Fulton           mailto:jim@zope.com       Python Powered!
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