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Revision as of 16:15, 25 March 2016 by Amrith (talk | contribs) (OpenStack applications (tc-approved))

This page tracks the progress of Python 3 effort porting for OpenStack.

IRC: #openstack-python3

Join the #openstack-python3 IRC channel on the Freenode network to discuss Python 3.

Python 3

Why should OpenStack move to Python 3 right now?

Python 3 is usually seen as the new Python version which breaks compatibility and raises new Unicode issues. Python 3 is much more than that. It’s a new clean language which has a more consistent syntax. It has many new features, not less than 15 new modules. Python 3 is already well supported by major Linux distributions, whereas Python 2.7 reached its end-of-life. Slowly, some bugs cannot be fixed in Python 2.7 anymore and are only fixed in the latest Python 3 release. Python 3 is now 5 years old and considered as a mature programming language.

Python 2: Python 2.6 support dropped, Python 2.7 only

OpenStack Liberty targets Python 2.7 and 3.4.

Python 2.6 support is being dropped in OpenStack since OpenStack Juno for servers. Python 2.6 support is currently kept in Oslo libraries and clients. See juno-cross-project-future-of-python etherpad.

Python 3.3 support is being dropped since OpenStack Liberty.

Python 2.6 is slowly being dropped in the whole OpenStack project, ex: Remove p26 job from DIB.

Python 2.6 support will be removed in Oslo and Clients clients for OpenStack Mitaka: Oslo libraries dropping python 2.6 compatability.

Port Python 2 code to Python 3

OpenStack project chose to use the same code base for Python 2 and Python 3. The Six: Python 2 and 3 Compatibility Library helps to write code working on both versions. OpenStack supported Python 2.6 for RHEL up to Juno, but not Python 2.5 and older. As we are targeting Python 3.4 and up, there is no need to avoid u'unicode' syntax. Do not use six.u('unicode').

Before you begin

If you're doing development with Ubuntu/Debian (and not using devstack with the USE_PYTHON flag set), then you'll need the following packages installed to run the py34 tox unit test targets in the projects:

   sudo apt-get install python3.4 python3.4-dev

sixer tool

The sixer tool helps to replace most basic patterns to add Python 3 compatibility and it respects OpenStack coding style.

Common patterns

  • Replace "for key in dict.iterkeys()" with "for key in dict"
  • Replace dict.iteritems() with dict.items()
  • Replace dict.itervalues() with dict.values()

Note: Replacing dict.iteritems()/.itervalues() with six.iteritems(dict)/six.itervalues(dict) was preferred in the past, but there was a discussion suggesting to avoid six for this. The overhead of creating a temporary list on Python 2 is negligible.

  • Replace iterator.next() with next(iterator)
  • Replace basestring with six.string_types
  • Replace unicode with six.text_type
  • Replace (str, unicode) with six.string_types
  • Replace (int, long) with six.integer_types
  • Replace func.func_name with func.__name__
  • Replace exceptions.OSError with OSError and remove "import exceptions"
  • map() and filter() if a list is needed on Python 3:
    • Replace map(func, data) with [func(item) for item in data]
    • Replace filter(lambda obj: test(obj), data) with [obj for obj in data if test(obj)]
    • Note: Usually, tests fail because map() or filter() objects have no length

Serialization: base64, JSON, etc.

  • [with oslo.serialization 1.10 or newer] Get the base64 module from oslo_serialization (from oslo_serialization import base64) to get functions:
    • oslo_serialization.base64.decode_as_bytes(encoded)
    • oslo_serialization.base64.decode_as_text(encoded, encoding='utf-8')
    • oslo_serialization.base64.encode_as_bytes(s, encoding='utf-8')
    • oslo_serialization.base64.encode_as_text(s, encoding='utf-8')
  • Replace text.encode('base64') and base64.b64encode(text) with:
    • base64.b64encode(text): only accept bytes and returns bytes,
    • or: oslo_serialization.base64.encode_as_bytes(text): accept bytes or Unicode and returns bytes
    • or: oslo_serialization.base64.encode_as_text(text): accept bytes and Unicode and returns Unicode
    • Warning: base64.encodestring(raw) adds a newline ("\n"), whereas encode_as_bytes() and encode_as_text() don't.
  • Replace raw.decode('base64') with:
    • base64.b64decode(raw): return bytes
    • oslo_serialization.base64.decode_as_bytes(encoded): accept bytes and Unicode, returns bytes
    • oslo_serialization.base64.decode_as_text(encoded): accept bytes and Unicode, returns Unicode


  • Replace raw.decode('hex') with binascii.unhexlify(raw)
  • Replace bytes.encode('hex') with binascii.hexlify(bytes)


  • [with oslo.serialization 1.10 or newer] Replace json.dumps(obj) with oslo_serialization.jsoutils.dump_as_bytes(obj)
  • Replace json.loads(obj) with oslo_serialization.jsoutils.loads(obj): it accepts bytes and Unicode, bytes is decoded from UTF-8. It avoids "if isinstance(obj, bytes): obj = obj.decode('utf-8')" which may require a second temporary variable.


To replaced contextlib.nested is to use contextlib.ExitStack. It's available on Python 2 using contextlib2.ExitStack. For contextlib.nested, nova/test.py defines:

if six.PY3:
    def nested(*contexts):
        with contextlib.ExitStack() as stack:
            yield [stack.enter_context(c) for c in contexts]
    nested = contextlib.nested

Another option to replaced contextlib.nested is to use the @mock.patch decorator. Example with nested function:

def test_thing(self):
   def do_test(...):

More options:


oslo.utils 3.5 has an oslo_utils.encodeutils.to_utf8() function to encode Unicode to UTF-8 and return bytes unchanged.

bytes.decode and unicode.encode

Python has a notion of "default encoding": sys.getdefaultencoding(). On Python 2, the default encoding is ASCII, whereas it is UTF-8 on Python 3.

Don't write data.decode() or text.encode() without parameter, because you will use a different encoding on Python 2 and Python 3.

Use an explicit encoding instead. Example: data.decode('utf-8') or text.encode('utf-8'). The right encoding depends on the use case, but UTF-8 is usually a good candidate (it is a superset of ASCII).


Olso Incubator has a function safe_decode() which can be used to decode a bytes string and pass text strings unchanged.

The default encoding is sys.stdin.encoding or sys.getdefaultencoding():

  • Python 3: the locale encoding, or UTF-8 if sys.stdin is "mocked" (io.StringIO instance)
  • Python 2: the locale encoding, or ASCII if stdin is not a TTY or if sys.stdin is "mocked" (StringIO.StringIO instance)

It's safer to explicit the encoding to not rely on the locale encoding and have the same behaviour even if sys.stdin is "mocked".

Safe usage:

  • safe_decode(data, 'utf-8'): decode bytes from UTF-8 or returns data unchanged if it's already a text string

Unsafe usage:

  • safe_decode(data)

By default, the decoder is strict. You can specify a different error handler using the optional errors parameter. Example: safe_decode(b'[\xff]', 'ascii', 'ignore') returns '[]'.


Olso Incubator has a function safe_encode() which can be used to encode a string. Its usage is tricky and you should understand how it works and which encodings are used.

  • safe_encode(text) encodes text to the output encoding
  • safe_encode(bytes) may decode the string and then reencode to a different encoding if input and output encodings are different

The default input encoding (incomding parameter) is sys.stdin.encoding or sys.getdefaultencoding():

  • Python 3: the locale encoding, or UTF-8 if sys.stdin is "mocked" (io.StringIO instance)
  • Python 2: the locale encoding, or ASCII if stdin is not a TTY or if sys.stdin is "mocked" (StringIO.StringIO instance)

The default output encoding (encoding parameter) is UTF-8.

It's safer to explicit the input encoding to not rely on the locale encoding and have the same behaviour even if sys.stdin is "mocked".

Safe usage:

  • safe_encode(data, incoming='utf-8'): encode text to UTF-8 or returns data unchanged if it's already a bytes string (since the input and output encoding are UTF-8)

Unsafe usage:

  • safe_encode(data)


  • safe_encode(b'\xe9', incoming='latin-1') returns b'\xc3\xa9'.

By default, the encoder and the decoder are strict. You can specify a different error handler using the optional errors parameter. Example: safe_encode(b'[\xff]', incoming='ascii', errors='ignore') returns b'[]'.

logging module and format exceptions

The exception_to_unicode(exc) function of oslo_utils.encodeutils is the recommanded way to format an exception to Unicode. This function works on Python 2 and Python 3 and it should avoid mojibake is most cases.

On Python 2, the logging module accepts bytes and text strings. On Python 3, it only accepts text strings. For example, logging.error(b'hello') logs b'hello' instead of 'hello'.

There is no clear rule for format exceptions yet. There are different choices depending on the project:

  • str(exc): native string, so use bytes on Python 2
  • six.text_type(exc): always use Unicode. It may raise unicode error depending on the exception, be careful. Example of such error in python 2: unicode(Exception("nonascii:\xe9")).
  • six.u(str(exc)): unsafe on Python 2 if str(exc) contains non-ASCII bytes, ex: unicode(str(Exception("\xff")))
  • LOG.exception(_LE("... %(exc)s ..."), {"exc": exc, ...})

Since logging functions expect text strings on Python 3, logged exceptions should be formatted using str(exc). Example: LOG.debug(str(exc)).


The HTTP protocol is based on bytes:

  • HTTP body contains bytes. For example, use io.BytesIO for a stream storing an HTTP body.
  • HTTPConnection.getresponse().read() returns bytes (in Python 3, str which is bytes in Python 2)
  • On Python 3, the http.client accepts text for HTTP headers: keys are encoded to ASCII and values to ISO 8859-1 (which is only a small subset of the Unicode charset)
  • It looks like Swift encodes internally HTTP headers to UTF-8 (directly using the UTF-8 encoding, not using a MIME encoding like =?UTF-8?Q?...?=. See the HTTP [RFC 2047 http://www.ietf.org/rfc/rfc2047.txt] and HTTP header should use what character encoding?

References to port Python 2 code to Python 3

Common pitfalls

What is a string ?

You should definitely not talk about "strings" in your commit logs/reviews. In Python 2, a 'string' is bytes; in Python 3, it's a Unicode text string. The following code snippet may help in understanding the difference:

Python 2:

   >>> type('foo')
   <type 'str'>
   >>> type(u'foo')
   <type 'unicode'>
   >>> type(b'foo')
   <type 'str'>
   >>> isinstance('foo', six.text_type)
   >>> isinstance(u'foo', six.text_type)
   >>> bytes is str
   >>> b'foo'[0]

Python 3:

   >>> type('foo')
   <class 'str'>
   >>> type(u'foo')
   <class 'str'>
   >>> type(b'foo')
   <class 'bytes'>
   >>> isinstance('foo', six.text_type)
   >>> isinstance(b'foo', six.text_type)
   >>> bytes is str
   >>> b'foo'[0]

tox/testr error: db type could not be determined

The "db type could not be determined" error comes from .testrepository/times.dbm used by testr.

Workaround: "rm -rf .testrepository/" and then run "tox -e py34" before running "tox -e py27". You only have to do this once. The problem only occurs with "tox -e py34" when .testrepository/ was created by Python 2.

Python 3 Status of OpenStack projects

Common Libraries (Oslo Projects)

See programs.yaml for the list of Common Libraries.

Project Python 3 compatibility Comment
cliff Yes
oslo.concurrency Yes
oslo-incubator Yes py34 gate is voting
oslo.config Yes
oslo.context Yes
oslo.db Yes

PyMySQL driver is now used by default for MySQL. setup.cfg contains the Python 3 classifier.

oslo.i18n Yes
oslo.log Yes
oslo.messaging Yes

oslo.messaging is now fully compatible with Python 3. The old (and now removed) Qpid transport was not compatible, the AMQP driver was ported recently.

The py34 check job is not more voting because of ubuntu still uses Python 3.4.0 which has a severe bug.

oslo.middleware Yes
oslo.rootwrap Yes

oslo.rootwrap 2.4 works on Python 3, but eventlet tests hangs on Python 3. It's now fixed in the development version. oslo.rootwrap has a non-voting python34 check job.

oslo.serialization Yes
oslosphinx  ? The project only contains two short .py files, it looks to be Python 3 compatible. Is Sphinx Python 3 compatible?
oslotest Yes
oslo.versionedobjects Yes
oslo.vmware Yes Supports Python 3 since oslo.vmware 0.13.0
oslo.utils Yes
pylockfile Yes
stevedore Yes
taskflow Yes

Development tools

Project Python 3 compatibility Comment
cookiecutter yes
hacking yes py33 gate is not voting
pbr yes
stackforge/python-jenkins yes py33 gate is voting
openstack-infra/jenkins-job-builder partial https://review.openstack.org/172238

OpenStack clients

Project Python 3 compatibility CI tests running? Python 3 classifiers ? Blocked by Comment
keystonemiddleware Yes Voting On PyPI python-memcached keystonemiddleware 1.6.1 supports Python 3.
python-barbicanclient Yes Voting On PyPI
python-ceilometerclient Yes Voting On PyPI
python-cinderclient Yes Voting On PyPI
python-fuelclient Yes voting Yes
python-glanceclient Yes Voting On PyPI
python-heatclient Yes Voting On PyPI
python-ironicclient Yes Voting On PyPI
python-keystoneclient Yes Voting On PyPI
python-manilaclient Yes Voting On PyPI
python-marconiclient Yes Voting On PyPI
python-novaclient Yes Voting On PyPII
python-neutronclient Yes Voting On PyPI
python-openstackclient Yes Voting On PyPI As of 0.9
python-saharaclient Yes Voting On PyPI
python-swiftclient Yes Voting On PyPI
python-tuskarclient Yes Voting On PyPI
python-troveclient Yes Voting On PyPI
python-watcherclient Yes Voting On PyPI
python-designateclient work in progress Voting No

OpenStack Libraries

Project Python 3 compatibility CI tests running? Python 3 classifiers ? Comment
django_openstack_auth Yes voting Yes

django_openstack_auth 2.0 is fully compatible with Python 3.

glance_store Yes voting Yes glance_store 0.7.0 added the Python 3 support.
neutron-lib Yes voting Yes
os-brick Yes voting Yes os-brick 0.3.2 added Python 3 support.
sqlalchemy-migrate Yes voting Yes
taskflow Yes voting Yes


There are two ways to express dependencies that should differ between Python 2.x and 3.x. We currently support using multiple requirements files, and will shortly be supporting and recommending the use of environment markers. Recent releases of all the tools in our ecosystem are needed for environment markers.


This approach generates a different requirements list depending on what Python version is running when the egg info is created (which goes into wheels and sdists). As a consequence this can't work with tox, publishing sdists to PyPI, or wheels. It is however useful for anything installing from git. To use it, create two requirements files:

  • requirements-py2.txt: all dependencies for Python 2 (not only dependencies specific to Python 2)
  • requirements-py3.txt: all dependencies for Python 3 (not only dependencies specific to Python 3)
  • (same for test-requirements.txt)

You have to edit tox.ini to specify the right requirements file. Extract of a tox.ini file:

deps = -r{toxinidir}/requirements-py3.txt

Environment markers

Environment markers provide a mini-language to express when a dependency is relevant. We hope the next release of pbr will support them. Recent pip, setuptools and wheel versions do support them, but until pbr exports the requirements metadata with them intact and structured correctly for setuptools, we can't use them anywhere.

When placed in a requirements.txt file, the markers are interpreted directly by pip in `pip install -r requirements.txt`, and indirectly via setuptools when installing an sdist or wheel (including `pip install .`. For instance:

futures; python_version < '3.2'

See also:

Oslo Messaging issue:

  • futures is not needed on Python 3, since concurrent.futures is now part of the Pyhon stdlib since Python 3.2
  • futures was added to requirements-py3.txt because tox creates the source tarball using Python 2 which reads requirements.txt
  • The correct fix would be to use environment markers on futures

Dependencies status

Porting status for global-requirement.txt.

Project Python 3 compatibility CI tests running? Python 3 classifiers ? Blocked by Comment
boto Yes N/A Yes See https://github.com/boto/boto3 (experimental) <- This seems dead, and https://github.com/boto/boto works with Python 3.x (since 2.32).
django-compressor Yes N/A Yes Requirements upgraded: https://review.openstack.org/94357
dnspython Yes N/A Yes Must use the Python 3 version, see https://github.com/rthalley/dnspython/issues/60
ecdsa Yes N/A Yes Py3 support merge before the 0.10 release (see https://github.com/warner/python-ecdsa/commits/master)
eventlet Yes Yes Yes eventlet 0.17.3 now fully support Python 3
jsonrpclib No N/A No The project seems dead :(
libvirt-python Yes N/A Yes
MySQL-Python No, but mysqlclient or PyMySQL are compatible N/A No


MySQL-Python: 2 pending pull requests for Python 3.

INADA Naoki, the maintainer of PyMySQL, wrote mysqlclient: fork of MySQL-Python using libmysqlclient.so which is Python 3 compatible. He recommends to use mysqlclient instead of MySQL-python even on Python 2. mysqlclient fixes some bugs, build issues and it support Python 3. For example: support MariaDB's libmysqlclient.so, support microsecond in TIME column.

PyMySQL is compatible with Python 3: see PyMySQL evaluation discussion to eventually replace mysql-python with PyMySQL in OpenStack.

netifaces Yes N/A Yes Patch sent by Victor Stinner (in private): netifaces_python3.patch, Debian has patches too. Python 3 support as of 0.10.4. Pushed to requirements: https://review.openstack.org/94358 .
nose-exclude Yes N/A No Python 3 is supported since nose-exclude 0.4.
nosehtmloutput No No No
  • nose-exclude (tests only)
  • openstack.nose-plugin
nosexcover No N/A On PyPI Python 3 support since 1.0.9
openstack.nose-plugin No No No
pam No for pam, Yes for simplepam NA No The fork simplepam works on Python 2 and 3
paramiko Yes N/A On PyPI Requirements upgraded: https://review.openstack.org/#/c/81132/
paste Yes N/A Yes Compatible with Python 3 since Paste 2.0
pycadf Yes Yes Yes
python-ldap No No No The project seems dead. See ldap3 which is Python 3 compatible (license: LGPL, one of the optional deps is BSD-4-Clause).
python-memcached Yes N/A Yes

python-memcached 1.56 is compatible with Python 3, but there are still some bugs: More Python 3 fixes (not part of python-memcached 1.57). These bugs impact running keystonemiddleware tests when the memcached server is not running. It can also impact a setup with multiple memcached servers.

qpid-python No No No Required if using oslo.messaging's qpid backend. That is the old pure python amqp 0-10 client library. That only speaks 0-10 and works with qpidd broker. It is used by the impl_qpid.py driver in oslo.messaging. That client is legacy - it isn't being ported to use AMQP 1.0.
pyngus Yes N/A No

pyngus 2.0 supports Python 3.

pyngus is required if using oslo.messaging's AMQP 1.0 driver. pyngus is a wrapper for proton and proton has not been ported to python 3 yet: see Proton issue #490.

Proton is a C library with various bindings in other languages. The language bindings are auto generated via the SWIG tool, plus a the python wrapper bits. All the python stuff is found under proton-c/bindings/python in the git tree. The first bit of work is to refactor the SWIG file cproton.i to work for both Python 2 and 3.

rtslib-fb No No No
Routes Yes Yes Yes Routes 2.2 works Python 2 and 3 using a single code base.
sphinxcontrib-docbookrestapi Yes Yes In the Git repo, not on PyPI
sphinxcontrib-httpdomain Yes N/A No
sphinxcontrib-pecanwsme No No No
thrift No No No
websockify Yes N/A Yes python3 works with the 0.7.0 version released on Jul 23, 2015

OpenStack applications (tc-approved)

OpenStack applications approved by the OpenStack Technical Committee.

Project Python 3 compatibility py34 gate Comments
ceilometer Yes voting
cinder Yes voting

cinder-python3 blueprint (written by Victor Stinner) has been accepted for Liberty. Patches: bp/cinder-python3 topic. Note: Commit message must use "Partial-Implements: blueprint cinder-python3" to be linked to the blueprint. Kendall Nelson, Ivan Kolodyazhny (core) and Eric Harney (core) prefer this syntax: see COMMIT_MSG.

glance Yes voting

Victor Stinner is working on porting Glance to Python3. Patches: Patches for glance (topic: py3).

ironic Yes voting

Python 3.4 unit tests are now being run for openstack/ironic. The unit tests are a voting job. Thanks to Victor Sergeyev for all of his work to update the Ironic code to make it pass the unit tests using Python 3.4: Run tests in py34 environment

heat Yes voting

Sirushti Murugesan wrote and implemented the spec Python34 Support (which was accepted for Liberty). Mitaka version will fully support Python 3. Great job Sirushti Murugesan who did almost all the work!

horizon Yes voting

George Peristerakis wrote Make Horizon python3.4 compatible in May 2015, the blueprint was approved. Patches: bp/porting-python3 topic.

neutron Yes voting

Porting to Python 3 spec (by Cyril Roelandt) accepted for Liberty, port in progress. Patches:

neutron-fwaas Yes voting
neutron-vpnaas Yes voting
sahara Yes voting
keystone work in progress voting

The spec Add spec for python-3 compatibility (by Morgan Fainberg) was accepted for Liberty. See also the blueprint python3 started by Dolph Mathews on 2014-07-22; David Stanek is working on it.

Patches: bp/python3 topic.

pysaml2 3.0 now supports Python 3.

Aslo blocked by ldappool and python-ldap. pyldap is a fork of python-ldap which adds Python 3 support. python-ldap may be replaced with ldap3, but it requires more work.

neutron-lbaas work in progress voting

Status at 2016-03-04: 1 unit test/806.

Patches: topic:bp/neutron-python3.

nova work in progress voting

Adding Python 3.4 support to Nova spec (by Victor Stinner) accepted for Liberty. Port in progress.

Patches: master (bp/nova-python3).

swift work in progress voting

openstack-dev: Plan to add Python 3 support to Swift.

Note for developers: PyECLib >= 1.0.8 is required by Python. To install liberasurecode (in /usr):

git clone https://bitbucket.org/tsg-/liberasurecode/
cd liberasurecode
/autogen.sh  && /configure --prefix=/usr && make && sudo make install

The python34 check job now pass. Python 3 unit tests require liberasurecode >= 1.0.9 and PyEClib >= 1.0.9. liberasurecode >= 1.0.9 is available in Ubuntu Precise, Ubuntu Trusty, Fedora 22, Fedora 23 and CentoOS 7.



trove Target: Newton no

Victor Stinner proposed the trove-python3 blueprint for Mitaka.

From Victor (3/17/2016): "I propose to discuss Python 3 before the summit. For example, prepare a concrete plan to port Trove to Python 3, list technical issues like MySQL-Python, etc."

Patches: search for the bp/trove-python3 topic.

Other OpenStack Applications and Projects

List of all OpenStack projects: projects.yaml.

Project Python 3 compatibility py34 gate Comments
aodh Yes voting
congress Yes voting

Random Stacker wrote a support-python3 blueprint. Patches: search for the topic bp/support-python3.

designate Yes voting

Pradeep Kumar Singh proposed the blueprint designate-py3 which was accepted for Liberty. Patches: topic:bp/designate-py3.

gnocchi Yes voting
manila Yes but... voting

Valeriy Ponomaryov wrote the py3-compatibility blueprint.

SSL tests are skipped because of the bug requests to SSL wrapped sockets hang while reading using py3.

octavia Yes voting
rally Yes voting A big thank to Andrey Kurilin for a lot of work in this direction
searchlight Yes voting
solum Yes voting

Victor Stinner proposed the blueprint solum-python3 which was approved. Patches: search for bp/solum-python3 topic (open reviews).

zaqar Yes voting
watcher Yes voting
barbican work in progress voting Pradeep Kumar Singh proposed the blueprint barbican-py3 for Liberty.

Patches: search for the bp/barbican-py3 topic.

mistral work in progress non voting

Update 2015-10-05: Renat Akhmerov wrote "Currently, we have 70-80 tests that fail on Python 3 which is the way better than it was a few weeks ago (it used to be ~500). (...) we're actively working on fixing all the tests for Python 3".

cue work in progress non-voting

Patches: search for topic py3.

magnum work in progress non-voting
murano work in progress non-voting

python-muranoclient and murano-dashboard fully support Python 3 and have jobs voting. murano and murano-agent are a work in progress, and have their jobs non-votin

Unsorted projects:

  • App Catalog
  • Chef OpenStack (Ruby)
  • Kolla: ~2100 lines of Python, but not "tox -e py27" target
  • OpenStack Ansible (Python): Ansible playbooks and roles for deployment
  • Puppet OpenStack (Ruby)
  • TripleO

Functional and Integration Tests

Doug Hellmann wrote a cross-project specification to run integration tests on Python 3: Enabling Python 3 for Application Integration Tests (spec approved for Liberty).

Patch for DevStack: Enable optional Python 3 support.

Projects wanting to run their existing functional test suite against their services on Python 3 should:-

  • Add the Python3.4 trove classifier to the setup.cfg configuration file of the respective service.
  • set USE_PYTHON3=True in Devstack's localrc config file before running stack.sh after the DevStack change is merged or cherry-pick until then.
  • set basepython = python3.4 in tox for the necessary functional/integration tests environment.

Then run tox -e<your functional test suite name>. Example:- tox -efunctional to run the functional the tests of a certain project.

Once the functional test suite is reliably passing against the service in a python 3.4 env, the trove classifiers must be updated along with a new gate job being added to the project.

Status of Python 3 in Linux distributions

  • ArchLinux already switched to Python 3 by default in 2011
  • Ubuntu wants to remove Python 2 from the default installation for Ubuntu 16.04 LTS: see (Python) Plans for 16.04.
  • Fedora schedules the switch in Fedora 23 (october 2015): Python 3 as the Default Implementation
  • RHEL: Python 3.3 and Python 3.4 are available on RHEL6 and RHEL7 using SCL.
  • CentOS: Python 3.3 and Python 3.4 are available on CentOS 6 and 7 using SCL (no Red Hat subscription needed, CentOS has its own flavor of SCL)
  • In Debian, the plan is to deprecate Python 2 in Stretch (aka: Debian 9, the next Stable Debian after Jessie) and to completely remove Python 2 for the Buster release of Debian (aka: Debian 10, to be release in approximatively 2019).

Reports at OpenStack Summits


Pycon Montreal 2014: Sprint Port OpenStack to Python 3

Enovance organized a sprint to Port OpenStack to Python 3 during 4 days: between April, 14 (Monday) and April, 17 (Thursday) 2014. See the page Python3/SprintPycon2014.