[Zope] store dict in session

[Dennis Schulz]

According to the zope book it should be possible to store dicts in session.
When I try to assign a dictionary to a ordinary zope 2 session, with 
lists there is no problem. why?:

        requestlist = {}
        for i in self.request.form:
            key = i
            value = self.request.form[i]
            requestlist[i] = self.request.form[i]
        sess = self.context.REQUEST.SESSION
        sess['pr_reqlist'] = requestlist

I get the following error:

Traceback (innermost last):

    * Module ZPublisher.Publish, line 196, in publish_module_standard
    * Module Products.PlacelessTranslationService.PatchStringIO, line
      34, in new_publish
    * Module ZPublisher.Publish, line 146, in publish
    * Module Zope2.App.startup, line 222, in zpublisher_exception_hook
    * Module ZPublisher.Publish, line 121, in publish
    * Module Zope2.App.startup, line 240, in commit
    * Module transaction._manager, line 96, in commit
    * Module transaction._transaction, line 380, in commit
    * Module transaction._transaction, line 378, in commit
    * Module transaction._transaction, line 433, in _commitResources
    * Module ZODB.Connection, line 484, in commit
    * Module ZODB.Connection, line 526, in _commit
    * Module ZODB.Connection, line 553, in _store_objects
    * Module ZODB.serialize, line 407, in serialize
    * Module ZODB.serialize, line 416, in _dump
    * Module copy_reg, line 69, in _reduce_ex

TypeError: can't pickle instancemethod objects (Also, the following 
error occurred while attempting to render the standard error message, 
please see the event log for full details: An operation previously 
failed, with traceback: File 
"C:\Python\Zope\Zope\lib\python\ZServer\PubCore\ZServerPublisher.py", 
line 23, in __init__ response=response) File 
"C:\Python\Zope\Zope\lib\python\ZPublisher\Publish.py", line 
395, in publish_module environ, debug, request, response) File 
"C:\Python\Zope\Zope\lib\python\ZPublisher\Publish.py", line 
196, in publish_module_standard response = publish(request, module_name, 
after_list, debug=debug) File 
"C:\Python\Zope\Instance\Products\PlacelessTranslationService\PatchStringIO.py", 
line 34, in new_publish x = Publish.old_publish(request, module_name, 
after_list, debug) File 
"C:\Python\Zope\Zope\lib\python\ZPublisher\Publish.py", line 
121, in publish transactions_manager.commit() File 
"C:\Python\Zope\Zope\lib\python\Zope2\App\startup.py", line 
240, in commit transaction.commit() File 
"C:\Python\Zope\Zope\lib\python\transaction\_manager.py", line 
96, in commit return self.get().commit(sub, deprecation_wng=False) File 
"C:\Python\Zope\Zope\lib\python\transaction\_transaction.py", 
line 380, in commit self._saveCommitishError() # This raises! File 
"C:\Python\Zope\Zope\lib\python\transaction\_transaction.py", 
line 378, in commit self._commitResources() File 
"C:\Python\Zope\Zope\lib\python\transaction\_transaction.py", 
line 433, in _commitResources rm.commit(self) File 
"C:\Python\Zope\Zope\lib\python\ZODB\Connection.py", line 484, 
in commit self._commit(transaction) File 
"C:\Python\Zope\Zope\lib\python\ZODB\Connection.py", line 526, 
in _commit self._store_objects(ObjectWriter(obj), transaction) File 
"C:\Python\Zope\Zope\lib\python\ZODB\Connection.py", line 553, 
in _store_objects p = writer.serialize(obj) # This calls __getstate__ of 
obj File "C:\Python\Zope\Zope\lib\python\ZODB\serialize.py", 
line 407, in serialize return self._dump(meta, obj.__getstate__()) File 
"C:\Python\Zope\Zope\lib\python\ZODB\serialize.py", line 416, 
in _dump self._p.dump(state) File 
"C:\Python\Zope\Python\lib\copy_reg.py", line 69, in 
_reduce_ex raise TypeError, "can't pickle %s objects" % 
base.__name__ TypeError: can't pickle instancemethod objects )