[Zope] Unauthorized exception when trying to access a list item

[Cameron Beattie]

I am trying to access a value in a list. The script getDIDS_list is passed a 
list called listoflists:
list = listoflists
ret = []
tup = (0,1,2)
factortup = (1,2)
factor = 2
for i in range(len(list)):
#   1 == 1
  if i in tup:
    if i in factortup:
       x = list[i] * factor
etc

The code is a bit strange due to my testing. However zope gets upset when 
trying to evaluate list[i]:

You are not allowed to access '1' in this context

a.. Module Products.PageTemplates.ZRPythonExpr, line 47, in __call__
__traceback_info__: context.getDIDS_list(listoflists = DIDs)
a.. Module Python expression "context.getDIDS_list(listoflists = DIDs)", 
line 1, in <expression>
a.. Module Shared.DC.Scripts.Bindings, line 311, in __call__
a.. Module Shared.DC.Scripts.Bindings, line 348, in _bindAndExec
a.. Module Products.PythonScripts.PythonScript, line 323, in _exec
a.. Module None, line 10, in getDIDS_list
<PythonScript at /Conversant/account/getDIDS_list>
Line 10
a.. Module AccessControl.ZopeGuards, line 71, in guarded_getitem
a.. Module AccessControl.ImplPython, line 529, in validate
a.. Module AccessControl.ImplPython, line 329, in validate

I've tried calling the script from the page template using 
here.getDIDS_list, container.getDIDS_list context.getDIDS_list but the 
problem persists. Am I accessing the list in the wrong way? Any advice would 
be appreciated.

Regards

Cameron