[Python-ideas] An exhaust() function for iterators

[David Mertz]

It is hard to imagine that doing this:

  for _ in side_effect_iter: pass

Could EVER realistically spend a significant share of its time in the loop
code.  Side effects almost surely need to do something that vastly
overpowers the cost of the loop itself (maybe some I/O, maybe some
computation), or there's no point in using a side-effect iterator.

I know you *could* technically write:

  def side_effect_iter(N, obj):
      for n in range(N):
          obj.val = n
          yield True

And probably something else whose only side effect was changing some value
that doesn't need real computation.  But surely writing that and exhausting
that iterator is NEVER the best way to code such a thing.

On the other hand, a more realistic one like this:

  def side_effect_iter(N):
      for n in range(N):
          val = complex_computation(n)
          write_to_slow_disk(val)
          yield True

Is going to take a long time in each iteration, and there's no reason to
care that the loop isn't absolutely optimal speed.



On Fri, Oct 11, 2013 at 11:29 AM, Neil Girdhar <mistersheik at gmail.com>wrote:

> This was also my thought.
>
>
> On Sunday, September 29, 2013 4:42:20 PM UTC-4, Serhiy Storchaka wrote:
>
>> 29.09.13 07:06, Clay Sweetser написав(ла):
>> > I would like to propose that this function, or one very similar to it,
>> > be added to the standard library, either in the itertools module, or
>> > the standard namespace.
>> > If nothing else, doing so would at least give a single *obvious* way
>> > to exhaust an iterator, instead of the several miscellaneous methods
>> > available.
>>
>> I prefer optimize the for loop so that it will be most efficient way (it
>> is already most obvious way).
>>
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