[Zope] Python script: how can I have a copy of a variable?

[p.t.]

Hi everybody,
I have a problem with Python scripts and SESSIONS I can't even understand, 
so I hope I can shortly explain it.

I put in REQUEST.status the currend process status.
I put in SESSION[processID]['status']['dataTable'] the name of a table.
Then I retrieve this name to the current status:
REQUEST['status'] = SESSION[processID]['status']

During the process I need to change the name of the table:
REQUEST['status']['dataTable'] = 'newName'

When going back to SESSION[processID]['status']['dataTable'], I've lost my 
oldName, and I find newName!

I've tryied shallow copy, argument passing, even renaming: nothing.
I've searched Python resouces, even read again the tutorial: no  clue.

One thing works, but its absolutely silly: to use different names, like:

SESSION[PROCESS_ID]['STATUS']['DATA_TABLE']

for storage session and then the usual naming during elaboration.

Now, what am I missing?
Any suggestion is welcome.
TIA,
	p.t.