[Python-ideas] Have max and min functions ignore None

[Michael Selik]

If None gets ignored, what about iterables that mix numbers and strings? A
comprehension handles the simple case relatively succinctly and also
handles more complex cases.

    max(x for x in iterable if isinstance(x, (int, float)))

If you prefer

    is_number = lambda obj: isinstance(obj, numbers.Number)
    max(filter(is_number, iterable))

On Tue, Dec 29, 2015 at 6:02 PM Gerald Britton <gerald.britton at gmail.com>
wrote:

> On *Tue Dec 29 06:22:58 EST 2015, Stephen D'Aprano wrote:*
>
>
>> So that's three perfectly reasonable behaviours: max(x, None) is an error
>> and should raise;
>> max(x, None) ignores None and returns x;
>> max(x, None) is unknown or missing and returns None
>> (or some other sentinel representing NA/Missing/Unknown).
>
>
> For comparison's sake, SQL ignores NULL when doing MAX:
>
> e.g.
>
> select max(val)
> from (values (1),(null)) v(val)
>
> returns
>
> 1
>
> In Python, None is sorta-kinda a bit like NULL in SQL, so one could make
> the argument that None should be handled similarly in min and max.  OTOH I
> wouldn't want to see Python implement 3-valued logic.
>
>
> --
> Gerald Britton, MCSE-DP, MVP
> LinkedIn Profile: http://ca.linkedin.com/in/geraldbritton
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