[Zope] calling python from template

[David Bear]

I want to call a python script from a page template but I don't know how to 'name' the script, ie I don't know how acquisition will find it.  

my script lives if /folderA/folderB
by page templated list is /folderA/folderB/folderC

I use <p tal:content="python:listObjects('departments', 'priority')">content of listObjects </p>

to call the listObjects script in folderB -- but zope isn't finding it.

what simple thing am I missing?