just chatting to one of the other developers, think we might be able to 
have a PythonInterpretor for each RuleSet, which should solve this 
issue. Otherwise whats potentially wrong with doing an exec with the 
following to emulate an expression:
        String tempText = stripOuterIndention( text );
        if (type.equals("eval"))
        {
            tempText = "return (" + tempText + ")";
        }
        this.text = newText.append(tempText).toString();


Mark
Oti wrote:

> IMHO you cannot eval an import statement:
>   Jython 2.1 on java1.4.2_05 (JIT: null)
>   Type "copyright", "credits" or "license" for more information.
>   >>> exec("from java.lang import String")
>   >>> eval("from java.lang import String")
>   Traceback (innermost last):
>     File "<console>", line 1, in ?
>     File "<string>", line 1  
>   	from java.lang import String
> 	^
>   SyntaxError: invalid syntax
>   >>> 
> 
> so you have to exec the imports first, e.g. like Jim suggested.
> 
> Best wishes,
> Oti.
> 
> --- Jim Adrig <jim@[...].com> wrote:
> 
>   
> 
> >If you are running these from Java, maybe something like what we do 
> >will work?
> >
> >First we 'add_package' since we have the cachedir stuff turned off:
> >
> >   // for Swing GUI building:
> >     PySystemState.add_package("javax");
> >     PySystemState.add_package("javax.swing");
> >     PySystemState.add_package("javax.swing.text");
> >     PySystemState.add_package("java.awt");         // Color, etc.
> >     PySystemState.add_package("java.awt.event");
> >
> >Then create an interpreter and 'execfile' all our standard 
> >imports/functions
> >
> >	  python.execfile( functionFileStream, functionFileName ); // pass
> >the 
> >name for parsing errors
> >
> >The 'functionFileStream' contains lots of things like:
> >
> >   from javax.swing import JCheckBox, JComboBox, JFrame, JMenuBar, 
> >JMenu, JMenuItem, JTable, JButton, JOptionPane, JRadioButton, 
> >JTextField
> >   from java.awt import Color, GridLayout, GridBagLayout
> >
> >
> >On Oct 21, 2004, at 12:45 PM, Mark Proctor wrote:
> >
> >    
> >
> >>I'm compiling expressions and blocks for use in our application, to
> >>      
> >>
> >>this we pre-append import statements declared elsewhere. It works
> >>      
> >>
> >fine 
> >    
> >
> >>when type is "exec" for blocks but fails when its "eval" for 
> >>expressions. Any ideas of how to get this to work?
> >>
> >>Mark
> >>
> >>   protected Interp(String text, Imports imports, String type)
> >>   {
> >>       this.origininalText = text;
> >>       StringBuffer newText = new StringBuffer();
> >>
> >>       if ((imports != null)&&(imports.getImportEntries() != null))
> >>       {
> >>           Iterator it =imports.getImportEntries().iterator();
> >>                     while (it.hasNext())
> >>           {                              ImportEntry importEntry =
> >>      
> >>
> >>(ImportEntry) it.next();
> >>               if (importEntry instanceof PythonImportEntry)
> >>               {
> >>                   newText.append(importEntry.getImportEntry());
> >>                   newText.append(";");
> >>                   newText.append(newline);
> >>               }
> >>           }                         }
> >>                            this.text = 
> >>newText.append(stripOuterIndention( text )).toString();
> >>
> >>       this.node = ( modType ) parser.parse( this.text, type );
> >>       this.code = Py.compile( this.node, "<jython>" );
> >>      
> >>
> 
> 
>   
>