>> [Alex measures speed improvements]
Guido> Great! This is a plus for iterator comprehensions (we need a Guido> better term BTW).
Here's an alternate suggestion. Instead of inventing new syntax, why not change the semantics of list comprehensions to be lazy? They haven't been in use that long, and while they are popular, the semantic tweakage would probably cause minimal disruption. In situations where laziness wasn't wanted, the most that a particular use would have to change (I think) is to pass it to list().