New submission from Jim Jewett <[email protected]>:
> http://hg.python.org/cpython/rev/0b5ce36a7a24
> changeset: 74515:0b5ce36a7a24
> + 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, :meth:`lower` would do nothing to ``'ß'``; :meth:`casefold`
> + converts it to ``"ss"``.
Perhaps add the recommendation to canonicalize as well.
A complete, but possibly too long, try is below:
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, :meth:`lower` would do nothing to ``'ß'``; :meth:`casefold` converts
it to ``"ss"``. Note that most case-insensitive matches should also match
compatibility equivalent characters.
The casefolding algorithm is described in section 3.13 of the Unicode Standard.
Per D146, a compatibility caseless match can be achieved by
from unicodedata import normalize
def caseless_compat(string):
nfd_string = normalize("NFD", string)
nfkd1_string = normalize("NFKD", nfd_string.casefold())
return normalize("NFKD", nfkd1_string.casefold())
----------
assignee: docs@python
components: Documentation
messages: 151644
nosy: Jim.Jewett, benjamin.peterson, docs@python
priority: normal
severity: normal
status: open
title: Further improve casefold documentation
versions: Python 3.3
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<http://bugs.python.org/issue13828>
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