[Python-ideas] [Python-Dev] minmax() function returning (minimum, maximum) tuple of a sequence

[Tal Einat]

Masklinn wrote:
> On 2010-10-11, at 02:55 , Zac Burns wrote:
>>
>> Unfortunately this solution seems incompatable with the implementations with
>> for loops in min and max (EG: How do you switch functions at the right
>> time?) So it might take some tweaking.
> As far as I know, there is no way to force lockstep iteration of arbitrary functions in Python. Though an argument could be made for adding coroutine capabilities to builtins and library functions taking iterables, I don't think that's on the books.
>
> As a result, this function would devolve into something along the lines of
>
>    def apply(iterable, *funcs):
>        return map(lambda c: c[0](c[1]), zip(funcs, tee(iterable, len(funcs))))
>
> which would run out of memory on very long or nigh-infinite iterables due to tee memoizing all the content of the iterator.

We recently needed exactly this -- to do several running calculations
in parallel on an iterable. We avoided using co-routines and just
created a RunningCalc class with a simple interface, and implemented
various running calculations as sub-classes, e.g. min, max, average,
variance, n-largest. This isn't very fast, but since generating the
iterated values is computationally heavy, this is fast enough for our
uses.

Having a standard method to do this in Python, with implementations
for common calculations in the stdlib, would have been nice.

I wouldn't mind trying to work up a PEP for this, if there is support
for the idea.

- Tal Einat