making python 2.3 not complain about generator expressions?

[Dan Christensen]

I'd like to be able to do something like:

if pythonversion >= 2.4:
    g = (x for x in [1,2,3])
else:
    g = iter([1,2,3])

But even though the first branch doesn't execute in python 2.3, the
parser still complains.

I can think of some tricks using strings and eval.  Is there anything
more elegant?

(By the way, what's the canonical way for a script to find out which
version of python it is running in?)

Dan