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

[Arnaud Delobelle]

On 15 October 2010 19:09, Ron Adam <rrr at ronadam.com> wrote:
>
>
> On 10/15/2010 12:27 PM, Georg Brandl wrote:
>>
>> Am 15.10.2010 19:13, schrieb Ron Adam:
>>
>>> [Tal also says]
>>>>
>>>> As Guido mentioned, there is never a reason to do max(value) where
>>>> value is not an iterable.
>>>
>>> Well, you can always avoid doing it, but that doesn't mean it wouldn't be
>>> nice to have sometimes.  Take a look at the following three coroutines
>>> that
>>> do the same exact thing.  Which is easier to read and which would be
>>> considered the more Pythonic.
>>>
>>>
>>> def xmin(*args, **kwds):
>>>      # Allow min to work with a single non-iterable value.
>>>      if len(args) == 1 and not hasattr(args[0], "__iter__"):
>>>          return min(args, **kwds)
>>>      else:
>>>          return min(*args, **kwds)
>>
>> I don't understand this function.  Why wouldn't you simply always call
>>
>>    return min(args, **kwds)
>>
>> ?
>
> Because it would always interpret a list of values as a single item.
>
> This function looks at args and if its a single value without an "__iter__"
> method, it passes it to min as min([value], **kwds) instead of min(value,
> **kwds).

But there are many iterable objects which are also comparable (hence
it makes sense to consider their min/max), for example strings.

So we get:

    xmin("foo", "bar", "baz") == "bar"
    xmin("foo", "bar") == "bar"

but:

   xmin("foo") == "f"

This will create havoc in your running min routine.

(Notice the same will hold for min() but at least you know that min(x)
considers x as an iterable and complains if it isn't)

--
Arnaud