[issue10587] Document the meaning of str methods

[Alexander Belopolsky]

Alexander Belopolsky <belopolsky at users.sourceforge.net> added the comment:

On Tue, Nov 30, 2010 at 1:53 PM, Martin v. Löwis <report at bugs.python.org> wrote:
..
> What is the issue that you are reporting? that the status quo should be documented, or that isalpha is wrong?
> These are independent - don't mix them.

This is a documentation issue.  I don't say that str.isalpha() is
necessarily wrong.  (If unicodedata had an isAlphabetic() menthod
defined as Lu + Ll + Lt + Lm + Lo, I would file a bug report for
that.)   Here, I just want to mention that proper str.isalpha()
definition is subject to debate and it being defined as Lu + Ll + Lt +
Lm + Lo may need to be marked as CPython implementation detail.  Note
that the Unicode book (sorry, don't have the page reference) advises
not to rely on catch-all APIs such as isAlphabetic(), but consult the
underlying properties directly.  I tend to agree with that because
some programs may want to treat say Roman numerals as letters and some
as numbers, so whether isAlphabetic() should include Nl category is
better left to the application.

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Python tracker <report at bugs.python.org>
<http://bugs.python.org/issue10587>
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