Case-insensitive string equality
MRAB
python at mrabarnett.plus.com
Thu Aug 31 19:53:38 EDT 2017
On 2017-08-31 16:29, Tim Chase wrote:
> On 2017-08-31 07:10, Steven D'Aprano wrote:
>> So I'd like to propose some additions to 3.7 or 3.8.
>
> Adding my "yes, a case-insensitive equality-check would be useful"
> with the following concerns:
>
> I'd want to have an optional parameter to take locale into
> consideration. E.g.
>
> "i".case_insensitive_equals("I") # depends on Locale
> "i".case_insensitive_equals("I", Locale("TR")) == False
> "i".case_insensitive_equals("I", Locale("US")) == True
>
> and other oddities like
>
> "ß".case_insensitive_equals("SS") == True
>
> (though casefold() takes care of that later one). Then you get
> things like
>
> "III".case_insensitive_equals("\N{ROMAN NUMERAL THREE}")
> "iii".case_insensitive_equals("\N{ROMAN NUMERAL THREE}")
> "FI".case_insensitive_equals("\N{LATIN SMALL LIGATURE FI}")
>
> where the decomposition might need to be considered. There are just
> a lot of odd edge-cases to consider when discussing fuzzy equality.
>
>> (1) Add a new string method,
>
> This is my preferred avenue.
>
>> Alternatively: how about a === triple-equals operator to do the
>> same thing?
>
> No. A strong -1 for new operators. This peeves me in other
> languages (looking at you, PHP & JavaScript)
>
>> (2) Add keyword-only arguments to str.find and str.index:
>>
>> casefold=False
>>
>> which does nothing if false (the default), and switches to a
>> case- insensitive search if true.
>
> I'm okay with some means of conveying the insensitivity to
> str.find/str.index but have no interest in list.find/list.index
> growing similar functionality. I'm meh on the "casefold=False"
> syntax, especially in light of my hope it would take a locale for the
> comparisons.
>
[snip]
What would you expect the result would be for:
"\N{LATIN SMALL LIGATURE FI}".case_insensitive_find("F")
"\N{LATIN SMALL LIGATURE FI}".case_insensitive_find("I)
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