Unicode probably won't make the correction, because of backwards
compatibility.  I do support the sentence suggested in Thorsten's most
recent reply.  Is expanding ligatures the only other normalization it does?

Ideally, we should also mention that it shifts to the canonical case, which
is usually (but not always) lowercase.  I think Cherokee is one that folds
to the upper case.

On Mon, Aug 24, 2020 at 11:02 AM Thorsten <report@bugs.python.org> wrote:

>
> Thorsten <mrsupertash@gmail.com> added the comment:
>
> I see. I found the documents. That's an issue. That usage is incorrect. It
> is still valid to upper case "ß" to SS since "ẞ" is fairly new as an
> official German character, but the other way around is not valid.
>
> As such the current sentence in documentation also just does not make
> sense.
>
> >"Since it is already lowercase, lower() would do nothing to 'ß'"
>
> Exactly. Why would it? It is nonsensical to change an already lowercase
> character with a lowercase function.
>
> Suggest to update to:
>
> "For example, the Unicode standard for German lower case letter 'ß'
> prescribes full casefolding to 'ss'. Since it is already lowercase, lower()
> would do nothing to 'ß'; casefold() converts it to 'ss'.
> In addition to full lowercasing, this function also expands ligatures, for
> example, 'fi' becomes 'fi'."
>
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> <https://bugs.python.org/issue13828>
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