mirror of https://github.com/python/cpython
172 lines
5.6 KiB
ReStructuredText
172 lines
5.6 KiB
ReStructuredText
:mod:`unicodedata` --- Unicode Database
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=======================================
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.. module:: unicodedata
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:synopsis: Access the Unicode Database.
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.. moduleauthor:: Marc-André Lemburg <mal@lemburg.com>
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.. sectionauthor:: Marc-André Lemburg <mal@lemburg.com>
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.. sectionauthor:: Martin v. Löwis <martin@v.loewis.de>
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.. index::
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single: Unicode
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single: character
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pair: Unicode; database
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This module provides access to the Unicode Character Database (UCD) which
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defines character properties for all Unicode characters. The data contained in
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this database is compiled from the `UCD version 6.2.0
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<http://www.unicode.org/Public/6.2.0/ucd>`_.
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The module uses the same names and symbols as defined by Unicode
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Standard Annex #44, `"Unicode Character Database"
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<http://www.unicode.org/reports/tr44/tr44-6.html>`_. It defines the
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following functions:
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.. function:: lookup(name)
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Look up character by name. If a character with the given name is found, return
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the corresponding character. If not found, :exc:`KeyError` is raised.
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.. versionchanged:: 3.3
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Support for name aliases [#]_ and named sequences [#]_ has been added.
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.. function:: name(chr[, default])
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Returns the name assigned to the character *chr* as a string. If no
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name is defined, *default* is returned, or, if not given, :exc:`ValueError` is
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raised.
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.. function:: decimal(chr[, default])
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Returns the decimal value assigned to the character *chr* as integer.
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If no such value is defined, *default* is returned, or, if not given,
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:exc:`ValueError` is raised.
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.. function:: digit(chr[, default])
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Returns the digit value assigned to the character *chr* as integer.
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If no such value is defined, *default* is returned, or, if not given,
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:exc:`ValueError` is raised.
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.. function:: numeric(chr[, default])
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Returns the numeric value assigned to the character *chr* as float.
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If no such value is defined, *default* is returned, or, if not given,
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:exc:`ValueError` is raised.
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.. function:: category(chr)
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Returns the general category assigned to the character *chr* as
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string.
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.. function:: bidirectional(chr)
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Returns the bidirectional category assigned to the character *chr* as
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string. If no such value is defined, an empty string is returned.
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.. function:: combining(chr)
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Returns the canonical combining class assigned to the character *chr*
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as integer. Returns ``0`` if no combining class is defined.
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.. function:: east_asian_width(chr)
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Returns the east asian width assigned to the character *chr* as
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string.
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.. function:: mirrored(chr)
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Returns the mirrored property assigned to the character *chr* as
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integer. Returns ``1`` if the character has been identified as a "mirrored"
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character in bidirectional text, ``0`` otherwise.
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.. function:: decomposition(chr)
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Returns the character decomposition mapping assigned to the character
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*chr* as string. An empty string is returned in case no such mapping is
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defined.
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.. function:: normalize(form, unistr)
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Return the normal form *form* for the Unicode string *unistr*. Valid values for
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*form* are 'NFC', 'NFKC', 'NFD', and 'NFKD'.
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The Unicode standard defines various normalization forms of a Unicode string,
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based on the definition of canonical equivalence and compatibility equivalence.
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In Unicode, several characters can be expressed in various way. For example, the
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character U+00C7 (LATIN CAPITAL LETTER C WITH CEDILLA) can also be expressed as
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the sequence U+0043 (LATIN CAPITAL LETTER C) U+0327 (COMBINING CEDILLA).
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For each character, there are two normal forms: normal form C and normal form D.
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Normal form D (NFD) is also known as canonical decomposition, and translates
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each character into its decomposed form. Normal form C (NFC) first applies a
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canonical decomposition, then composes pre-combined characters again.
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In addition to these two forms, there are two additional normal forms based on
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compatibility equivalence. In Unicode, certain characters are supported which
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normally would be unified with other characters. For example, U+2160 (ROMAN
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NUMERAL ONE) is really the same thing as U+0049 (LATIN CAPITAL LETTER I).
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However, it is supported in Unicode for compatibility with existing character
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sets (e.g. gb2312).
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The normal form KD (NFKD) will apply the compatibility decomposition, i.e.
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replace all compatibility characters with their equivalents. The normal form KC
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(NFKC) first applies the compatibility decomposition, followed by the canonical
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composition.
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Even if two unicode strings are normalized and look the same to
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a human reader, if one has combining characters and the other
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doesn't, they may not compare equal.
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In addition, the module exposes the following constant:
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.. data:: unidata_version
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The version of the Unicode database used in this module.
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.. data:: ucd_3_2_0
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This is an object that has the same methods as the entire module, but uses the
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Unicode database version 3.2 instead, for applications that require this
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specific version of the Unicode database (such as IDNA).
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Examples:
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>>> import unicodedata
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>>> unicodedata.lookup('LEFT CURLY BRACKET')
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'{'
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>>> unicodedata.name('/')
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'SOLIDUS'
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>>> unicodedata.decimal('9')
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9
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>>> unicodedata.decimal('a')
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Traceback (most recent call last):
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File "<stdin>", line 1, in ?
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ValueError: not a decimal
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>>> unicodedata.category('A') # 'L'etter, 'u'ppercase
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'Lu'
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>>> unicodedata.bidirectional('\u0660') # 'A'rabic, 'N'umber
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'AN'
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.. rubric:: Footnotes
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.. [#] http://www.unicode.org/Public/6.1.0/ucd/NameAliases.txt
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.. [#] http://www.unicode.org/Public/6.1.0/ucd/NamedSequences.txt
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