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Internationalized Domain Names in Applications (IDNA)
=====================================================
Support for the Internationalised Domain Names in Applications
(IDNA) protocol as specified in `RFC 5891 <http://tools.ietf.org/html/rfc5891>`_.
This is the latest version of the protocol and is sometimes referred to as
“IDNA 2008”.
This library also provides support for Unicode Technical Standard 46,
`Unicode IDNA Compatibility Processing <http://unicode.org/reports/tr46/>`_.
This acts as a suitable replacement for the “encodings.idna” module that
comes with the Python standard library, but only supports the
old, deprecated IDNA specification (`RFC 3490 <http://tools.ietf.org/html/rfc3490>`_).
Basic functions are simply executed:
.. code-block:: pycon
# Python 3
>>> import idna
>>> idna.encode('ドメイン.テスト')
b'xn--eckwd4c7c.xn--zckzah'
>>> print(idna.decode('xn--eckwd4c7c.xn--zckzah'))
ドメイン.テスト
# Python 2
>>> import idna
>>> idna.encode(u'ドメイン.テスト')
'xn--eckwd4c7c.xn--zckzah'
>>> print idna.decode('xn--eckwd4c7c.xn--zckzah')
ドメイン.テスト
Packages
--------
The latest tagged release version is published in the PyPI repository:
.. image:: https://badge.fury.io/py/idna.svg
:target: http://badge.fury.io/py/idna
Installation
------------
To install this library, you can use pip:
.. code-block:: bash
$ pip install idna
Alternatively, you can install the package using the bundled setup script:
.. code-block:: bash
$ python setup.py install
This library works with Python 2.6 or later, and Python 3.3 or later.
Usage
-----
For typical usage, the ``encode`` and ``decode`` functions will take a domain
name argument and perform a conversion to A-labels or U-labels respectively.
.. code-block:: pycon
# Python 3
>>> import idna
>>> idna.encode('ドメイン.テスト')
b'xn--eckwd4c7c.xn--zckzah'
>>> print(idna.decode('xn--eckwd4c7c.xn--zckzah'))
ドメイン.テスト
You may use the codec encoding and decoding methods using the
``idna.codec`` module:
.. code-block:: pycon
# Python 2
>>> import idna.codec
>>> print u'домена.испытание'.encode('idna')
xn--80ahd1agd.xn--80akhbyknj4f
>>> print 'xn--80ahd1agd.xn--80akhbyknj4f'.decode('idna')
домена.испытание
Conversions can be applied at a per-label basis using the ``ulabel`` or ``alabel``
functions if necessary:
.. code-block:: pycon
# Python 2
>>> idna.alabel(u'测试')
'xn--0zwm56d'
Compatibility Mapping (UTS #46)
+++++++++++++++++++++++++++++++
As described in `RFC 5895 <http://tools.ietf.org/html/rfc5895>`_, the IDNA
specification no longer normalizes input from different potential ways a user
may input a domain name. This functionality, known as a “mapping”, is now
considered by the specification to be a local user-interface issue distinct
from IDNA conversion functionality.
This library provides one such mapping, that was developed by the Unicode
Consortium. Known as `Unicode IDNA Compatibility Processing <http://unicode.org/reports/tr46/>`_,
it provides for both a regular mapping for typical applications, as well as
a transitional mapping to help migrate from older IDNA 2003 applications.
For example, “Königsgäßchen” is not a permissible label as *LATIN CAPITAL
LETTER K* is not allowed (nor are capital letters in general). UTS 46 will
convert this into lower case prior to applying the IDNA conversion.
.. code-block:: pycon
# Python 3
>>> import idna
>>> idna.encode(u'Königsgäßchen')
...
idna.core.InvalidCodepoint: Codepoint U+004B at position 1 of 'Königsgäßchen' not allowed
>>> idna.encode('Königsgäßchen', uts46=True)
b'xn--knigsgchen-b4a3dun'
>>> print(idna.decode('xn--knigsgchen-b4a3dun'))
königsgäßchen
Transitional processing provides conversions to help transition from the older
2003 standard to the current standard. For example, in the original IDNA
specification, the *LATIN SMALL LETTER SHARP S* (ß) was converted into two
*LATIN SMALL LETTER S* (ss), whereas in the current IDNA specification this
conversion is not performed.
.. code-block:: pycon
# Python 2
>>> idna.encode(u'Königsgäßchen', uts46=True, transitional=True)
'xn--knigsgsschen-lcb0w'
Implementors should use transitional processing with caution, only in rare
cases where conversion from legacy labels to current labels must be performed
(i.e. IDNA implementations that pre-date 2008). For typical applications
that just need to convert labels, transitional processing is unlikely to be
beneficial and could produce unexpected incompatible results.
``encodings.idna`` Compatibility
++++++++++++++++++++++++++++++++
Function calls from the Python built-in ``encodings.idna`` module are
mapped to their IDNA 2008 equivalents using the ``idna.compat`` module.
Simply substitute the ``import`` clause in your code to refer to the
new module name.
Exceptions
----------
All errors raised during the conversion following the specification should
raise an exception derived from the ``idna.IDNAError`` base class.
More specific exceptions that may be generated as ``idna.IDNABidiError``
when the error reflects an illegal combination of left-to-right and right-to-left
characters in a label; ``idna.InvalidCodepoint`` when a specific codepoint is
an illegal character in an IDN label (i.e. INVALID); and ``idna.InvalidCodepointContext``
when the codepoint is illegal based on its positional context (i.e. it is CONTEXTO
or CONTEXTJ but the contextual requirements are not satisfied.)
Testing
-------
The library has a test suite based on each rule of the IDNA specification, as
well as tests that are provided as part of the Unicode Technical Standard 46,
`Unicode IDNA Compatibility Processing <http://unicode.org/reports/tr46/>`_.
The tests are run automatically on each commit at Travis CI:
.. image:: https://travis-ci.org/kjd/idna.svg?branch=master
:target: https://travis-ci.org/kjd/idna
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