[Python-Dev] accumulator display syntax

[Phillip J. Eby]

At 08:57 AM 10/21/03 -0500, Skip Montanaro wrote:

>     >> [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().

If you make it a list that's lazy, it doesn't lose the memory allocation 
overhead for the list.  If I understand Alex's benchmarks, making a lazy 
list would end up being *slower* than list comprehension is now.

I previously proposed a different solution earlier in this thread, where 
you get a pseudo-list that, if iterated, runs the underlying generator 
function.  But there were issues with possible side-effects (not to mention 
reiterability) of the underlying iterator on which the comprehension was based.