# 4.10 `unicodedata` -- Unicode Database

This module provides access to the Unicode Character Database which defines character properties for all Unicode characters. The data in this database is based on the UnicodeData.txt file version 3.2.0 which is publically available from ftp://ftp.unicode.org/.

The module uses the same names and symbols as defined by the UnicodeData File Format 3.2.0 (see http://www.unicode.org/Public/UNIDATA/UnicodeData.html). It defines the following functions:

`lookup`( | name)

  Look up character by name. If a character with the given name is found, return the corresponding Unicode character. If not found, `KeyError` is raised.

`name`( | unichr[, default])

  Returns the name assigned to the Unicode character unichr as a string. If no name is defined, default is returned, or, if not given, `ValueError` is raised.

`decimal`( | unichr[, default])

  Returns the decimal value assigned to the Unicode character unichr as integer. If no such value is defined, default is returned, or, if not given, `ValueError` is raised.

`digit`( | unichr[, default])

  Returns the digit value assigned to the Unicode character unichr as integer. If no such value is defined, default is returned, or, if not given, `ValueError` is raised.

`numeric`( | unichr[, default])

  Returns the numeric value assigned to the Unicode character unichr as float. If no such value is defined, default is returned, or, if not given, `ValueError` is raised.

`category`( | unichr)

  Returns the general category assigned to the Unicode character unichr as string.

`bidirectional`( | unichr)

  Returns the bidirectional category assigned to the Unicode character unichr as string. If no such value is defined, an empty string is returned.

`combining`( | unichr)

  Returns the canonical combining class assigned to the Unicode character unichr as integer. Returns `0` if no combining class is defined.

`mirrored`( | unichr)

  Returns the mirrored property of assigned to the Unicode character unichr as integer. Returns `1` if the character has been identified as a ``mirrored'' character in bidirectional text, `0` otherwise.

`decomposition`( | unichr)

  Returns the character decomposition mapping assigned to the Unicode character unichr as string. An empty string is returned in case no such mapping is defined.

`normalize`( | form, unistr)

  Return the normal form form for the Unicode string unistr. Valid values for form are 'NFC', 'NFKC', 'NFD', and 'NFKD'.

  The Unicode standard defines various normalization forms of a Unicode string, based on the definition of canonical equivalence and compatibility equivalence. In Unicode, several characters can be expressed in various way. For example, the character U+00C7 (LATIN CAPITAL LETTER C WITH CEDILLA) can also be expressed as the sequence U+0043 (LATIN CAPITAL LETTER C) U+0327 (COMBINING CEDILLA).

  For each character, there are two normal forms: normal form C and normal form D. Normal form D (NFD) is also known as canonical decomposition, and translates each character into its decomposed form. Normal form C (NFC) first applies a canonical decomposition, then composes pre-combined characters again.

  In addition to these two forms, there two additional normal forms based on compatibility equivalence. In Unicode, certain characters are supported which normally would be unified with other characters. For example, U+2160 (ROMAN NUMERAL ONE) is really the same thing as U+0049 (LATIN CAPITAL LETTER I). However, it is supported in Unicode for compatibility with existing character sets (e.g. gb2312).

  The normal form KD (NFKD) will apply the compatibility decomposition, i.e. replace all compatibility characters with their equivalents. The normal form KC (NFKC) first applies the compatibility decomposition, followed by the canonical composition.

  New in version 2.3.

In addition, the module exposes the following constant:

`unidata_version`
  The version of the Unicode database used in this module.

  New in version 2.3.