CPython >>> str(None) 'None' >>> unicode(None) u'None' >>> type(unicode(None)) <type 'unicode'> >>> type(unicode('ble')) <type 'unicode'> IronPython >>> str(None) 'None' >>> unicode(None) 'None' >>> type(unicode(None)) <type 'str'> >>> type(unicode('ble')) <type 'str'> Is this the correct behavior? - Sylvain