Groups > comp.lang.python > #81912

Re: How is max supposed to work, especially key.

From	Terry Reedy <tjreedy@udel.edu>
Subject	Re: How is max supposed to work, especially key.
Date	2014-12-04 10:47 -0500
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Newsgroups	comp.lang.python
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On 12/4/2014 5:35 AM, Albert van der Horst wrote:

> 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.

The key function serves the same purpose as with sort.  It define a 
custom ordering of items, not the values returned.  'x < y' is defined 
as key(x) < key(y), where the comparison of keys uses the standard (and 
for numbers, natural) built-in ordering.  So max returns the max value 
according to the order you define with the key function.  The default 
key is the identity function, so the default order is the builtin order.

-- 
Terry Jan Reedy

Thread

How is max supposed to work, especially key. albert@spenarnc.xs4all.nl (Albert van der Horst) - 2014-11-27 17:34 +0000
  Re: How is max supposed to work, especially key. Peter Otten <__peter__@web.de> - 2014-11-27 19:01 +0100
    Re: How is max supposed to work, especially key. albert@spenarnc.xs4all.nl (Albert van der Horst) - 2014-12-04 10:09 +0000
      Re: How is max supposed to work, especially key. Chris Angelico <rosuav@gmail.com> - 2014-12-04 21:18 +1100
        Re: How is max supposed to work, especially key. albert@spenarnc.xs4all.nl (Albert van der Horst) - 2014-12-04 10:35 +0000
          Re: How is max supposed to work, especially key. Jussi Piitulainen <jpiitula@ling.helsinki.fi> - 2014-12-04 12:51 +0200
          Re: How is max supposed to work, especially key. Peter Otten <__peter__@web.de> - 2014-12-04 12:31 +0100
          Re: How is max supposed to work, especially key. Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2014-12-04 23:03 +1100
          Re: How is max supposed to work, especially key. Terry Reedy <tjreedy@udel.edu> - 2014-12-04 10:47 -0500
      Re: How is max supposed to work, especially key. Jussi Piitulainen <jpiitula@ling.helsinki.fi> - 2014-12-04 12:45 +0200
        Re: How is max supposed to work, especially key. Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2014-12-04 22:55 +1100
          Re: How is max supposed to work, especially key. Jussi Piitulainen <jpiitula@ling.helsinki.fi> - 2014-12-04 14:58 +0200
      Re: How is max supposed to work, especially key. Peter Otten <__peter__@web.de> - 2014-12-04 12:24 +0100
      Re: How is max supposed to work, especially key. random832@fastmail.us - 2014-12-04 09:09 -0500

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