Author steven.daprano
Recipients Calvin Davis, steven.daprano, terry.reedy
Date 2020-07-11.04:32:06
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Message-id <1594441926.52.0.833852741382.issue41276@roundup.psfhosted.org>
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In your first example, `min([(-5, 2), (0, 2)])` the min() function compares the two tuples and finds that the first one is lexicographically smaller:

    py> (-5, 2) < (0, 2)
    True

so (-5, 2) is considered the minimum. In the second example, using the key function compares 2 with 2, but since they are equal, the *first* tuple wins and is considered the minimum, and so using the key function doesn't change the result.

In your third example, after reversing the list, you have `min([(0, 2), (-5, 2)])` and the min() function compares the two tuples and finds the *second* tuple is the smaller:

    py> (0, 2) < (-5, 2)
    False

But in the fourth example, using the key function, yet again the comparison compares 2 with 2 and finds them equal, and so the *first* tuple wins and (0, 2) is declared the minimum.

When using the key function, only the second item of the tuple is looked at; the first item is ignored. So the difference between 0 and -5 is irrelevant, and the tie is decided by which element was seen first.
History
Date User Action Args
2020-07-11 04:32:06steven.dapranosetrecipients: + steven.daprano, terry.reedy, Calvin Davis
2020-07-11 04:32:06steven.dapranosetmessageid: <1594441926.52.0.833852741382.issue41276@roundup.psfhosted.org>
2020-07-11 04:32:06steven.dapranolinkissue41276 messages
2020-07-11 04:32:06steven.dapranocreate