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slugid.py - Compressed UUIDs for python ======================================= .. image:: https://tools.taskcluster.net/lib/assets/taskcluster-120.png |Build Status| |Coverage Status| |License| |pypi Version| |Downloads| A python module for generating v4 UUIDs and encoding them into 22 character URL-safe base64 slug representation (see `RFC 4648 sec. 5`_). Slugs are url-safe base64 encoded v4 uuids, stripped of base64 ``=`` padding. There are two methods for generating slugs - ``slugid.v4()`` and ``slugid.nice()``. - The ``slugid.v4()`` method returns a slug from a randomly generated v4 uuid. - The ``slugid.nice()`` method returns a v4 slug which conforms to a set of "nice" properties. At the moment the only "nice" property is that the slug starts with ``[A-Za-f]``, which in turn implies that the first (most significant) bit of its associated uuid is set to 0. The purpose of the ``slugid.nice()`` method is to support having slugids which can be used in more contexts safely. Regular slugids can safely be used in urls, and for example in AMQP routing keys. However, slugs beginning with ``-`` may cause problems when used as command line parameters. In contrast, slugids generated by the ``slugid.nice()`` method can safely be used as command line parameters. This comes at a cost to entropy (121 bits vs 122 bits for regular v4 slugs). Slug consumers should consider carefully which of these two slug generation methods to call. Is it more important to have maximum entropy, or to have slugids that do not need special treatment when used as command line parameters? This is especially important if you are providing a service which supplies slugs to unexpecting tool developers downstream, who may not realise the risks of using your regular v4 slugs as command line parameters, especially since this would arise only as an intermittent issue (one time in 64). Generated slugs take the form ``[A-Za-z0-9_-]{22}``, or more precisely: - ``slugid.v4()`` slugs conform to ``[A-Za-z0-9_-]{8}[Q-T][A-Za-z0-9_-][CGKOSWaeimquy26-][A-Za-z0-9_-]{10}[AQgw]`` - ``slugid.nice()`` slugs conform to ``[A-Za-f][A-Za-z0-9_-]{7}[Q-T][A-Za-z0-9_-][CGKOSWaeimquy26-][A-Za-z0-9_-]{10}[AQgw]`` RFC 4122 defines the setting of 6 bits of the v4 UUID which implies v4 slugs provide 128 - 6 = 122 bits entropy. Due to the (un)setting of the first bit of "nice" slugs, nice slugs provide therefore 121 bits entropy. Usage ----- .. code-block:: python import slugid # Generate "nice" URL-safe base64 encoded UUID version 4 (random) slug = slugid.nice() # a8_YezW8T7e1jLxG7evy-A # Alternative, if slugs will not be used as command line parameters slug = slugid.v4() # -9OpXaCORAaFh4sJRk7PUA # Get python uuid.UUID object uuid = slugid.decode(slug) # Compress to slug again assert(slug == slugid.encode(uuid)) RNG Characteristics ------------------- UUID generation is performed by the built-in python `uuid library`_ which does not document its randomness, but falls back to system uuid-generation libraries where available, then urandom, then random. Therefore generated slugids match these rng characteristics. License ------- The ``slugid`` library is released on the MPL 2.0 license, see the ``LICENSE`` for complete license. Testing ------- .. code-block:: bash pip install -r requirements.txt tox Publishing ---------- To republish this library to pypi.python.org, update the version number in ``slugid/__init__.py``, commit it, push to github, and then run: .. code-block:: bash # delete stale versions rm -rf dist # build source package python setup.py sdist # publish it twine upload -s dist/* .. _RFC 4648 sec. 5: http://tools.ietf.org/html/rfc4648#section-5 .. _uuid library: https://docs.python.org/2/library/uuid.html .. |Build Status| image:: https://travis-ci.org/taskcluster/slugid.py.svg?branch=master :target: http://travis-ci.org/taskcluster/slugid.py .. |Coverage Status| image:: https://coveralls.io/repos/taskcluster/slugid.py/badge.svg?branch=master&service=github :target: https://coveralls.io/github/taskcluster/slugid.py?branch=master .. |License| image:: https://img.shields.io/badge/license-MPL%202.0-orange.svg :target: https://github.com/taskcluster/slugid.py/blob/master/LICENSE .. |pypi Version| image:: https://img.shields.io/pypi/v/slugid.svg :target: https://pypi.python.org/pypi/slugid .. |Downloads| image:: https://img.shields.io/pypi/dm/slugid.svg :target: https://pypi.python.org/pypi/slugid