vincent wehren wrote:
>
>| > If you don't care about the year, why not just "normalize" the year
>| > to all be the same using the replace method of the date instance?
>|
>| That's a very bad idea. In my example, this would work, but in "reality"
>| I don't sort datetime objects, of course! (Is there any real application
>| where you want to do that?)
>|
>| Instead, I'm sorting "Person" objects using a "birthday" attribute.
>| Since I use these Person objects also in other places, they should never
>| be modified without just to be sorted. In general, the number side effects
>| should always be minimized.
>
> Can you explain where you see a modification to the orginal object
> happening?
> (or in any of the other solutions proposed for that matter...)
Sorry, my fault. I didn't read carefully enough. X-)
> Not here I hope:
>
>| > datesNorm = [obj.replace(year=1900) for obj in (dates)]
>| > datesNorm.sort()
While you don't change the original objects, there's still a problem since
you're sorting the normalized values. However, I want to sort the original
list (i.e. the list of "Person" objects).
But that's not a real problem if one normalizes in a key function:
def key_birthday(d):
return d.replace(year=1900)
...
dates.sort(key=key_birthday)
..as suggested in other followups of my posting.
>| Nevertheless, I think you idea is very interesting. Is there any "real"
>| application where normalizing just for sorting would be reasonable?
>
> How about a case-insensitive sort of strings? (uppering being the
> normalization step)
> Or getting rid of accented / special characters before sorting.
> These sound like fairly straight-forward use cases to me ;)
For your solution these are good examples. But my question was, whether
normalizing first, and just sorting the normalized values (not the original
values) is reasonable.
I.e., when I sort some strings case-insensitive, I don't want my resulting
(sorted) list to contain only lowercase string. But that's what I would
get if I used the algorithm you described above.
Greets,
--
Volker Grabsch
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