Guido> I expect that most iterator comprehensions (we need a better Guido> term!)
You didn't like "lazy list comprehensions"?
No, because list comprehensions are no longer the fundamental building blocks. Generator expression sounds good to me now.
Guido> We can quibble about whether double parentheses are needed, ...
You haven't convinced me that you're not going to want to toss out one of the two comprehension syntaxes and only retain the lazy semantics in Py3k.
Too many double negatives. :-) Right now I feel like keeping both syntaxes, but declaring list comprehensions syntactic sugar for list(generator expression).
If that's the case and the current list comprehension syntax is better than the current crop of proposals, why even add (lazy list|iterator) comprehensions now? Just make do without them until Py3k and make all list comprehensions lazy at that point. There will be enough other bullets to bite that this shouldn't be a big deal (many programs will probably require significant rewriting anyway).
It's likely that generator experssions won't make it into Python 2.x for any x, just because of the effort to get the community to accept new syntax in general. --Guido van Rossum (home page: http://www.python.org/~guido/)