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https://github.com/avian2/unidecode

ASCII transliterations of Unicode text - GitHub mirror
https://github.com/avian2/unidecode

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ASCII transliterations of Unicode text - GitHub mirror

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README 

        
Unidecode, lossy ASCII transliterations of Unicode text

=======================================================



It often happens that you have text data in Unicode, but you need to

represent it in ASCII. For example when integrating with legacy code that

doesn't support Unicode, or for ease of entry of non-Roman names on a US

keyboard, or when constructing ASCII machine identifiers from human-readable

Unicode strings that should still be somewhat intelligible. A popular example

of this is when making an URL slug from an article title.



**Unidecode is not a replacement for fully supporting Unicode for strings in

your program. There are a number of caveats that come with its use,

especially when its output is directly visible to users. Please read the rest

of this README before using Unidecode in your project.**



In most of examples listed above you could represent Unicode characters as

``???`` or ``\\15BA\\15A0\\1610``, to mention two extreme cases. But that's

nearly useless to someone who actually wants to read what the text says.



What Unidecode provides is a middle road: the function ``unidecode()`` takes

Unicode data and tries to represent it in ASCII characters (i.e., the

universally displayable characters between 0x00 and 0x7F), where the

compromises taken when mapping between two character sets are chosen to be

near what a human with a US keyboard would choose.



The quality of resulting ASCII representation varies. For languages of

western origin it should be between perfect and good. On the other hand

transliteration (i.e., conveying, in Roman letters, the pronunciation

expressed by the text in some other writing system) of languages like

Chinese, Japanese or Korean is a very complex issue and this library does

not even attempt to address it. It draws the line at context-free

character-by-character mapping. So a good rule of thumb is that the further

the script you are transliterating is from Latin alphabet, the worse the

transliteration will be.



Generally Unidecode produces better results than simply stripping accents from

characters (which can be done in Python with built-in functions). It is based

on hand-tuned character mappings that for example also contain ASCII

approximations for symbols and non-Latin alphabets.



**Note that some people might find certain transliterations offending.** Most

common examples include characters that are used in multiple languages. A user

expects a character to be transliterated in their language but Unidecode uses a

transliteration for a different language. It's best to not use Unidecode for

strings that are directly visible to users of your application. See also the

*Frequently Asked Questions* section for more info on common problems.



This is a Python port of ``Text::Unidecode`` Perl module by Sean M. Burke

.



Module content

--------------



This library contains a function that takes a string object, possibly

containing non-ASCII characters, and returns a string that can be safely

encoded to ASCII::



    >>> from unidecode import unidecode

    >>> unidecode('kožušček')

    'kozuscek'

    >>> unidecode('30 \U0001d5c4\U0001d5c6/\U0001d5c1')

    '30 km/h'

    >>> unidecode('\u5317\u4EB0')

    'Bei Jing '



You can also specify an *errors* argument to ``unidecode()`` that determines

what Unidecode does with characters that are not present in its transliteration

tables. The default is ``'ignore'`` meaning that Unidecode will ignore those

characters (replace them with an empty string). ``'strict'`` will raise a

``UnidecodeError``. The exception object will contain an *index* attribute that

can be used to find the offending character. ``'replace'`` will replace them

with ``'?'`` (or another string, specified in the *replace_str* argument).

``'preserve'`` will keep the original, non-ASCII character in the string. Note

that if ``'preserve'`` is used the string returned by ``unidecode()`` will not

be ASCII-encodable!::



    >>> unidecode('\ue000') # unidecode does not have replacements for Private Use Area characters

    ''

    >>> unidecode('\ue000', errors='strict')

    Traceback (most recent call last):

    ...

    unidecode.UnidecodeError: no replacement found for character '\ue000' in position 0



A utility is also included that allows you to transliterate text from the

command line in several ways. Reading from standard input::



    $ echo hello | unidecode

    hello



from a command line argument::



    $ unidecode -c hello

    hello



or from a file::



    $ unidecode hello.txt

    hello



The default encoding used by the utility depends on your system locale. You can

specify another encoding with the ``-e`` argument. See ``unidecode --help`` for

a full list of available options.



Requirements

------------



Nothing except Python itself. Unidecode supports Python 3.7 or later.



You need a Python build with "wide" Unicode characters (also called "UCS-4

build") in order for Unidecode to work correctly with characters outside of

Basic Multilingual Plane (BMP). Common characters outside BMP are bold, italic,

script, etc. variants of the Latin alphabet intended for mathematical notation.

Surrogate pair encoding of "narrow" builds is not supported in Unidecode.



If your Python build supports "wide" Unicode the following expression will

return True::



    >>> import sys

    >>> sys.maxunicode > 0xffff

    True



See `PEP 261 `_ for details

regarding support for "wide" Unicode characters in Python.



Installation

------------



To install the latest version of Unidecode from the Python package index, use

these commands::



    $ pip install unidecode



To install Unidecode from the source distribution and run unit tests, use::



    $ python setup.py install

    $ python setup.py test



Frequently asked questions

--------------------------



German umlauts are transliterated incorrectly

    Latin letters "a", "o" and "u" with diaeresis are transliterated by

    Unidecode as "a", "o", "u", *not* according to German rules "ae", "oe",

    "ue". This is intentional and will not be changed. Rationale is that these

    letters are used in languages other than German (for example, Finnish and

    Turkish). German text transliterated without the extra "e" is much more

    readable than other languages transliterated using German rules. A

    workaround is to do your own replacements of these characters before

    passing the string to ``unidecode()``.



Japanese Kanji is transliterated as Chinese

    Same as with Latin letters with accents discussed in the answer above, the

    Unicode standard encodes letters, not letters in a certain language or

    their meaning. With Japanese and Chinese this is even more evident because

    the same letter can have very different transliterations depending on the

    language it is used in. Since Unidecode does not do language-specific

    transliteration (see next question), it must decide on one. For certain

    characters that are used in both Japanese and Chinese the decision was to

    use Chinese transliterations. If you intend to transliterate Japanese,

    Chinese or Korean text please consider using other libraries which do

    language-specific transliteration, such as `Unihandecode

    `_.



Unidecode should support localization (e.g. a language or country parameter, inspecting system locale, etc.)

    Language-specific transliteration is a complicated problem and beyond the

    scope of this library. Changes related to this will not be accepted. Please

    consider using other libraries which do provide this capability, such as

    `Unihandecode `_.



Unidecode should automatically detect the language of the text being transliterated

    Language detection is a completely separate problem and beyond the scope of

    this library.



Unidecode should use a permissive license such as MIT or the BSD license.

    The maintainer of Unidecode believes that providing access to source code

    on redistribution is a fair and reasonable request when basing products on

    voluntary work of many contributors. If the license is not suitable for

    you, please consider using other libraries, such as `text-unidecode

    `_.



Unidecode produces completely wrong results (e.g. "u" with diaeresis transliterating as "A 1/4 ")

    The strings you are passing to Unidecode have been wrongly decoded

    somewhere in your program. For example, you might be decoding utf-8 encoded

    strings as latin1. With a misconfigured terminal, locale and/or a text

    editor this might not be immediately apparent. Inspect your strings with

    ``repr()`` and consult the

    `Unicode HOWTO `_.



Why does Unidecode not replace \\u and \\U backslash escapes in my strings?

    Unidecode knows nothing about escape sequences. Interpreting these sequences

    and replacing them with actual Unicode characters in string literals is the

    task of the Python interpreter. If you are asking this question you are

    very likely misunderstanding the purpose of this library. Consult the

    `Unicode HOWTO `_ and possibly

    the ``unicode_escape`` encoding in the standard library.



I've upgraded Unidecode and now some URLs on my website return 404 Not Found.

    This is an issue with the software that is running your website, not

    Unidecode. Occasionally, new versions of Unidecode library are released

    which contain improvements to the transliteration tables. This means that

    you cannot rely that ``unidecode()`` output will not change across

    different versions of Unidecode library. If you use ``unidecode()`` to

    generate URLs for your website, either generate the URL slug once and store

    it in the database or lock your dependency of Unidecode to one specific

    version.



Some of the issues in this section are discussed in more detail in `this blog

post `_.



Performance notes

-----------------



By default, ``unidecode()`` optimizes for the use case where most of the strings

passed to it are already ASCII-only and no transliteration is necessary (this

default might change in future versions).



For performance critical applications, two additional functions are exposed:



``unidecode_expect_ascii()`` is optimized for ASCII-only inputs (approximately

5 times faster than ``unidecode_expect_nonascii()`` on 10 character strings,

more on longer strings), but slightly slower for non-ASCII inputs.



``unidecode_expect_nonascii()`` takes approximately the same amount of time on

ASCII and non-ASCII inputs, but is slightly faster for non-ASCII inputs than

``unidecode_expect_ascii()``.



Apart from differences in run time, both functions produce identical results.

For most users of Unidecode, the difference in performance should be

negligible.



Source

------



You can get the latest development version of Unidecode with::



    $ git clone https://www.tablix.org/~avian/git/unidecode.git



There is also an official mirror of this repository on GitHub at

https://github.com/avian2/unidecode



Contact

-------



Please make sure to read the `Frequently asked questions`_ section above before

contacting the maintainer.



Bug reports, patches and suggestions for Unidecode can be sent to

[email protected].



Alternatively, you can also open a ticket or pull request at

https://github.com/avian2/unidecode



Copyright

---------



Original character transliteration tables:



Copyright 2001, Sean M. Burke , all rights reserved.



Python code and later additions:



Copyright 2024, Tomaž Šolc 



This program is free software; you can redistribute it and/or modify it

under the terms of the GNU General Public License as published by the Free

Software Foundation; either version 2 of the License, or (at your option)

any later version.



This program is distributed in the hope that it will be useful, but WITHOUT

ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or

FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for

more details.



You should have received a copy of the GNU General Public License along

with this program; if not, write to the Free Software Foundation, Inc., 51

Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.  The programs and

documentation in this dist are distributed in the hope that they will be

useful, but without any warranty; without even the implied warranty of

merchantability or fitness for a particular purpose.



..

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