Fredrik Lundh wrote:
> Bengt Richter wrote:
>
>> Are you thinking of something like lines from a file, where there might
>> be chunky buffering? ISTM that wouldn't matter if the same next method
>> was called. Here we have multiple references to the same iterator. Isn't
>> e.g. buiding a plain tuple defined with evaluation one element at a time
>> left to right?
>
> yeah, but what says that the iterator has to be called during tuple
> construction?
>
> while 1:
> for each sequence:
> # optimize cache behaviour!
> grab up to N items from each iterator
> M = length of shortest output list
> for i in range(M):
> build tuple and append
> if M != N:
> break
Wouldn't every attempt to introduce such an optimization be shot down by the
likes of
def exponential():
for i in xrange(sys.maxint):
time.sleep(2**i)
yield "whatever"
def const():
for i in xrange(5): yield i
zip(exponential(), const())
To say it another way, aren't the problems that can be created by not
specifying zip() behaviour in a way that allows the zip(it, it) trick worse
than those you want to prevent?
Peter
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