规范化 Unicode

在 Python 中，是否有一种标准方法来规范化 unicode 字符串，以便它只理解可以用来表示它的最简单的 unicode 实体？

我的意思是，能够把像 ['LATIN SMALL LETTER A', 'COMBINING ACUTE ACCENT']这样的序列翻译成 ['LATIN SMALL LETTER A WITH ACUTE']的东西？

看看问题出在哪里:

>>> import unicodedata
>>> char = "á"
>>> len(char)
1
>>> [ unicodedata.name(c) for c in char ]
['LATIN SMALL LETTER A WITH ACUTE']

但现在:

>>> char = "á"
>>> len(char)
2
>>> [ unicodedata.name(c) for c in char ]
['LATIN SMALL LETTER A', 'COMBINING ACUTE ACCENT']

当然，我可以迭代所有的字符并进行手动替换，等等，但这并不高效，而且我很确定我会错过一半的特殊情况，并出现错误。

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小开

Yes, there is.

unicodedata.normalize(form, unistr)

You need to select one of the four normalization forms.

小开
最佳答案

The unicodedata module offers a .normalize() function, you want to normalize to the NFC form. An example using the same U+0061 LATIN SMALL LETTER - U+0301 A COMBINING ACUTE ACCENT combination and U+00E1 LATIN SMALL LETTER A WITH ACUTE code points you used:

>>> print(ascii(unicodedata.normalize('NFC', '\u0061\u0301')))
'\xe1'
>>> print(ascii(unicodedata.normalize('NFD', '\u00e1')))
'a\u0301'

(I used the ascii() function here to ensure non-ASCII codepoints are printed using escape syntax, making the differences clear).

NFC, or 'Normal Form Composed' returns composed characters, NFD, 'Normal Form Decomposed' gives you decomposed, combined characters.

The additional NFKC and NFKD forms deal with compatibility codepoints; e.g. U+2160 ROMAN NUMERAL ONE is really just the same thing as U+0049 LATIN CAPITAL LETTER I but present in the Unicode standard to remain compatible with encodings that treat them separately. Using either NFKC or NFKD form, in addition to composing or decomposing characters, will also replace all 'compatibility' characters with their canonical form.

Here is an example using the U+2167 ROMAN NUMERAL EIGHT codepoint; using the NFKC form replaces this with a sequence of ASCII V and I characters:

>>> unicodedata.normalize('NFC', '\u2167')
'Ⅷ'
>>> unicodedata.normalize('NFKC', '\u2167')
'VIII'

Note that there is no guarantee that composed and decomposed forms are commutative; normalizing a combined character to NFC form, then converting the result back to NFD form does not always result in the same character sequence. The Unicode standard maintains a list of exceptions; characters on this list are composable, but not decomposable back to their combined form, for various reasons. Also see the documentation on the Composition Exclusion Table.


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