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Devyn Collier Johnson devyncjohnson at
Sat Jul 20 14:20:30 CEST 2013

On 07/19/2013 09:13 PM, Chris Angelico wrote:
> On Sat, Jul 20, 2013 at 11:04 AM, Devyn Collier Johnson
> <devyncjohnson at> wrote:
>> On 07/19/2013 07:09 PM, Dave Angel wrote:
>>> On 07/19/2013 06:08 PM, Devyn Collier Johnson wrote:
>>>> On 07/19/2013 01:59 PM, Steven D'Aprano wrote:
>>>       <snip>
>>>> As for the case-insensitive if-statements, most code uses Latin letters.
>>>> Making a case-insensitive-international if-statement would be
>>>> interesting. I can tackle that later. For now, I only wanted to take
>>>> care of Latin letters. I hope to figure something out for all characters.
>>> Once Steven gave you the answer, what's to figure out?  You simply use
>>> casefold() instead of lower().  The only constraint is it's 3.3 and later,
>>> so you can't use it for anything earlier.
>>> """
>>> str.casefold()
>>> Return a casefolded copy of the string. Casefolded strings may be used for
>>> caseless matching.
>>> Casefolding is similar to lowercasing but more aggressive because it is
>>> intended to remove all case distinctions in a string. For example, the
>>> German lowercase letter 'ß' is equivalent to "ss". Since it is already
>>> lowercase, lower() would do nothing to 'ß'; casefold() converts it to "ss".
>>> The casefolding algorithm is described in section 3.13 of the Unicode
>>> Standard.
>>> New in version 3.3.
>>> """
>> Chris Angelico said that casefold is not perfect. In the future, I want to
>> make the perfect international-case-insensitive if-statement. For now, my
>> code only supports a limited range of characters. Even with casefold, I will
>> have some issues as Chris Angelico mentioned. Also, "ß" is not really the
>> same as "ss".
> Well, casefold is about as good as it's ever going to be, but that's
> because "the perfect international-case-insensitive comparison" is a
> fundamentally impossible goal. Your last sentence hints as to why;
> there is no simple way to compare strings containing those characters,
> because the correct treatment varies according to context.
> Your two best options are: Be case sensitive (and then you need only
> worry about composition and combining characters and all those
> nightmares - the ones you have to worry about either way), or use
> casefold(). Of those, I prefer the first, because it's safer; the
> second is also a good option.
> ChrisA
Thanks everyone (especially Chris Angelico and Steven D'Aprano) for all 
of your helpful suggests and ideas. I plan to implement casefold() in 
some of my programs.


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