Internationalized Domain Names in Applications (IDNA)

A library to support the Internationalised Domain Names in Applications (IDNA) protocol as specified in RFC 5891. This version of the protocol is often referred to as “IDNA2008” and can produce different results from the earlier standard from 2003.

The library is also intended to act as a suitable drop-in replacement for the “encodings.idna” module that comes with the Python standard library but currently only supports the older 2003 specification.

Its basic functions are simply executed:

>>> 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

The latest tagged release version is published in the PyPI repository:

To install this library, you can use PIP:

$ pip install idna

Alternatively, you can install the package using the bundled setup script:

$ python setup.py install

This library should work with Python 2.7, and Python 3.3 or later.

For typical usage, the encode and decode functions will take a domain name argument and perform a conversion to an A-label or U-label respectively.

>>> 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

You may use the codec encoding and decoding methods using the idna.codec module.

>>> 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:

>>> idna.alabel(u'测试')
'xn--0zwm56d'

As described in RFC 5895, the IDNA specification no longer including mappings from different forms of input that a user may enter, to the form that is provided to the IDNA functions. This functionality is now a local user-interface issue distinct from the IDNA functionality.

The Unicode Consortium has developed one such user-level mapping, known as Unicode IDNA Compatibility Processing. It provides for both transitional mapping and non-transitional mapping described in this document.

>>> import idna
>>> idna.encode(u'Königsgäßchen')
...
idna.core.InvalidCodepoint: Codepoint U+004B at position 1 of u'K\xf6nigsg\xe4\xdfchen' not allowed
>>> idna.encode(u'Königsgäßchen', uts46=True)
'xn--knigsgchen-b4a3dun'
>>> idna.encode(u'Königsgäßchen', uts46=True, transitional=True)
'xn--knigsgsschen-lcb0w'

Note that implementors should use transitional processing with caution as the outputs of the functions may differ from what is expected, as noted in the example.

Function calls from the Python built-in encodings.idna module are mapping 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.

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.)

The library has a test suite based on each rule of the IDNA specification, as well as test that are provided as part of the Unicode Technical Standard 46, Unicode IDNA Compatibility Processing.

The tests are run automatically on each commit to the master branch of the idna git repository at Travis CI: