[Zope] Testing types in TAL

[Alec Mitchell]

So I've run into a minor TAL problem recently.  I'm trying to test to see if 
an object is a List or a Tuple (or more generally a sequence that isn't a 
string), but can't figure out a way.  I've tried the following:

   python:isinstance(obj, list)
doesn't work (it doesn't recoginze 'list' as a 'class, type or tuple of 
classes and types'), strangely:
   python:isinstance(obj, str)
works ('str' is ok, but not 'list' or 'tuple'?).  Also:
   python:list(obj)
works despite the fact that 'list' is not recognized as a class!

using:
   python:type(obj) is type([])
fails because type() is not recognized in TAL.

using:
   python:hasattr(obj, '__iter__')
fails also, though I'm not sure why (probably TAL doesn't bother with 
variables starting with '_').

And it's impossible to pull 'ListType' etc. in using modules['types'], because 
of the lack of security assertions on the 'types' module.

There must be a way to do a simple type check for a tuple without a python 
script, no?  Right now I'm using:

tal:define="dictish nocall:obj/keys|nothing;
            listish python:not dictish and len(obj) and (len(obj[0]) != 1)"

Which is far too kludgy, brittle, and plain incorrect for my liking.

Thanks,
Alec Mitchell