How is max supposed to work, especially key.

[Albert van der Horst]

In article <mailman.16552.1417688329.18130.python-list at python.org>,
Chris Angelico  <rosuav at gmail.com> wrote:
>On Thu, Dec 4, 2014 at 9:09 PM, Albert van der Horst
><albert at spenarnc.xs4all.nl> wrote:
>>>If there is more than one item with the maximum calculated the first is
>>>given, so for your attempt
>>>
>>>max(xrange(100,200), key=lambda i: i%17==0 )
>>
>>>
>>>the values False, False, True, False, ... are calculated and because
>>>
>>>>>> True > False
>>>True
>>>
>>>the first one with a True result is returned.
>>>
>>
>> So in that case max doesn't return the maximum (True), but instead
>> something else.
>>
>> Useful as that function may be, it shouldn't have been called max.
>>
>> I don't blame myself for being misled.
>
>If lots of them are equally the largest, by whatever definition of
>largest you have, it has to do one of three things:
>
>1) Raise an exception
>2) Return multiple items (either as a tuple, or a generator, or something)
>3) Pick one of them and return it.
>
>Python's max() does the third, and for the picking part, uses the
>first one it comes across - a decent way to do it.
>
>If there's no clear maximum, it can't do any better than that. It's
>still returning something for which there is no greater.

I agree that it is a useful function and that it is doing
the right thing. What is wrong is the name.
I refer to the fact that it is not returning the maximum.
It returns the iterator value that leads to the maximum.
A function that doesn't return a maximum shouldn't be called
maximum.

>
>ChrisA
-- 
Albert van der Horst, UTRECHT,THE NETHERLANDS
Economic growth -- being exponential -- ultimately falters.
albert at spe&ar&c.xs4all.nl &=n http://home.hccnet.nl/a.w.m.van.der.horst