[Zope] Strange behavior with TAL and python: expressions

[Floyd May]

Great and mighty Zope gurus,

I have a template which calls a macro.  Within the template, I
tal:define a variable, 'form'.  Within the macro, the 'form' variable
(which is an FSForm object) is defined as None unless I access it
using python expressions.  If I attempt to do anything with attributes
of 'form', I get an AttributeError indicating that the NoneType
object, form, doesn't have the attribute that I'm looking for. 
However, I can use 'form' any way I want inside the template that
calls the macro.  It seems that the macro call somehow lost part of
the information associated with the 'form' variable.

I worked around the problem by defining form using a python expression
instead of a pure TALES expression.  I was also able to work around
the issue by accessing 'form' within the macro using python
expressions instead of TALES.  Why would this happen?  Is this
expected?

I'm using Zope 2.7.5 and Formulator 1.9.  I'm not sure what other
products to list here; this seems like a ZPT-related thing.  Please
let me know if there is any more information I can provide.

Thanks!

--
Floyd May
Senior Systems Analyst
CTLN - CareerTech Learning Network
fmay at okcareertech.org