Recently, as part of our push to ship only Python 3 on the Ubuntu 12.10
desktop, I've helped several projects update their internationalization
(i18n) support. I've seen lots of instances of suboptimal Python 2 i18n code,
which leads to liberal sprinkling of cargo culted .decode() and
.encode() calls simply to avoid the dreaded UnicodeError s. These get
worse when the application or library is ported to Python 3 because then even
the workarounds aren't enough to prevent nasty failures in non-ASCII
environments (i.e. the non-English speaking world majority :).
Let's be honest though, the problem is not because these developers are crappy
coders! In fact, far from it, the folks I've talked with are really really
smart, experienced Pythonistas. The fundamental problem is Python 2's 8-bit
string type which doubles as a bytes type, and the terrible API of the
built-in Python 2 gettext module, which does its utmost to sabotage your
Python 2 i18n programs. I take considerable blame for the latter, since I
wrote the original version of that module. At the time, I really didn't
understand unicodes (this is probably also evident in the mess I made of the
email package). Oh, to really have access to Guido's time machine.
The good news is that we now know how to do i18n right, especially in a
bilingual Python 2/3 world, and the Python 3 gettext module fixes the most
egregious problems in the Python 2 version. Hopefully this article does some
measure of making up for my past sins.
Stop right here and go watch Ned Batchelder's talk from PyCon 2012 entitled
Pragmatic Unicode, or How Do I Stop the Pain? It's the single best
description of the background and effective use of Unicode in Python you'll
ever see. Ned does a brilliant job of …
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So, now all the world now knows that my suggested code name for Ubuntu 12.10,
Qwazy Quahog, was not chosen by Mark. Oh well, maybe I'll have more luck
with Racy Roadrunner.
In any case, Ubuntu 12.04 LTS is to be released any day now so it's time
for my semi-annual report on Python plans for Ubuntu. I seem to write about
this every cycle, so 12.10 is no exception. We've made some fantastic
progress, but now it's time to get serious.
For Ubuntu 12.10, we've made it a release goal to have Python 3 only on the
desktop CD images. The usual caveats apply: Python 2.7 isn't going away; it
will still probably always be available in the main archive. This release
goal also doesn't affect other installation CD images, such as server, or
other Ubuntu flavors. The relatively modest goal then only affects
packages for the standard desktop CD images, i.e. the alternative installation
CD and the live CD.
Update 2012-04-25: To be crystal clear, if you depend on Python 2.7, the
only thing that changes for you is that after a fresh install from the
desktop CD on a new machine, you'll have to explicitly apt-get install
*python2.7. After that, everything else will be the same.
This is ostensibly an effort to port a significant chunk of Ubuntu to Python
3, but it really is a much wider, Python-community driven effort. Ubuntu has
its priorities, but I personally want to see a world where Python 3 rules the
day, and we can finally start scoffing at Python 2 :).
Still, that leaves us with about 145 binary packages (and many fewer source
packages) to port. There are a few categories of packages to consider:
- Already ported and available.
- This is …
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Time for another installment of my ongoing mission to convert the world to
Python 3! This time, a little Debian packaging-fu for modifying an existing
Python 2 package to include support for Python 3 from the same source package.
Today, I added a python3-feedparser package to Ubuntu Precise. What's
interesting about this is that, despite various reported problems, upstream
feedparser 5.1 claims to support Python 3, via 2to3 conversion. And indeed
it does (although the test suite does not).
Before today, Ubuntu had feedparser 5.0.1 in its archive, and while some
work has been done to update the Debian package to 5.1, this has not been
released. The uninteresting precursor to Python 3 packaging was to upgrade
the Ubuntu version of the python-feedparser source package to 5.1. I'll spare
you the boring details about missing data files in the upstream tarball, and
other problems, since they don't really relate to the Python 3 effort.
The first step was to verify that feedparser 5.1 works with Python 3.2 in a
virtualenv, and indeed it does. This is good news because it means that the
setup.py does the right thing, which is always the best way to start
supporting Python 3. I've found that it's much easier to build a solid Debian
package if you have a solid setup.py in upstream to begin with.
Now, what I'd like to do is to give you a recipe for modifying your existing
debian/ directory files to add Python 3 support to a package that already
exists for Python 2. This is a little trickier for feedparser because it used
an older debhelper standard, and carried some crufty old stuff in its
rules file. My first step was to update this to debhelper compatibility
level 8 …
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My last post on Python 3 porting got some really great responses, and I've
learned a lot from the feedback I've seen. I'm here to rather briefly outline
a few additional tips and tricks that folks have sent me and that I've learned
by doing other ports since then. Please keep them coming, either in the blog
comments or to me via email. Or better yet, blog about your experiences
yourself and I'll link to them from here.
One of the big lessons I'm trying to adopt is to support Python 3 in
pure-Python code with a single code base. Specifically, I'm trying to avoid
using 2to3 as much as possible. While I think 2to3 is an excellent tool that
can make it easier to get started supporting both Python 2 and Python 3 from a
single branch of code, it does have some disadvantages. The biggest problem
with 2to3 is that it's slow; it can take a long time to slog through your
Python code, which can be a significant impediment to your development
velocity. Another 2to3 problem is that it doesn't always play nicely with
other development tools, such as python setup.py test and virtualenv, and
you occasionally have to write additional custom fixers for conversion that
2to3 doesn't handle.
Given that almost all the code I'm writing these days targets Python 2.6 as
the minimal supported Python 2 version, 2to3 may just be unnecessary. With my
dbus-python port to Python 3, and with my own flufl packages, I'm
experimenting with ignoring 2to3 and trying to write one code base for all of
Python 2.6, 2.7, and 3.2. My colleague Michael Foord has been pretty
successful with this approach going back all the way to Python 2.4, so 2.6 as
a …
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Yesterday, I completed my port of dbus-python to Python 3, and submitted
my patch upstream. While I've yet to hear any feedback from Simon about my
patch, I'm fairly confident that it's going in the right direction. This
version should allow existing Python 2 applications to run largely unchanged,
and minimizes the differences that clients will have to make to use the Python
3 version.
Some of the changes are specific to the dbus-python project, and I included
a detailed summary of those changes and my rationale behind them. There
are lots of good lessons learned during this porting exercise that I want to
share with you, have a discussion about, and see if there aren't things we
core Python developers can do in Python 3.3 to make it even easier to migrate
to Python 3.
First, some background. D-Bus is a freedesktop.org project for same-system
interprocess communication, and it's an essential component of any Linux
desktop. The D-Bus system and C API are mature and well-defined, and there
are bindings available for many programming language, Python included of
course. The existing dbus-python package is only compatible with Python 2,
and most recommendations are to use the Gnome version of Python bindings
should you want to use D-Bus with Python 3. For us in Ubuntu, this isn't
acceptable though because we must have a solution that supports KDE and
potentially even non-UI based D-Bus Python servers. Several ports of
dbus-python to Python 3 have been attempted in the past, but none have been
accepted upstream, so naturally I took it as a challenge to work on a new
version of the port. After some discussion with the upstream maintainer Simon
McVittie, I had a few requirements in mind:
- One code base for both Python 2 and Python 3 …
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Earlier this month, I attended UDS-P (the Ubuntu Developers Summit for 12.04
Precise Pangolin). 12.04 is an LTS release, or Long Term Support,
meaning it will be officially supported on both the desktop and server for
five years.
During the summit we reiterated our plans for Python on Ubuntu, both for
12.04 LTS, and our vision of Python two years from now for the next LTS,
14.04. I'm here to provide an update from my last report, which was written
after UDS-O for 11.10.
As per those previous plans, we've removed Python 2.6 from Ubuntu 12.04. Now
you have only Python 2.7 and 3.2. Dropping Python 2.6 may cause some
inconvenience for data centers which like to upgrade only between LTS's but
don't want to have to upgrade both their operation system and their Python
version. Canonical services such as Launchpad and Landscape fall into this
camp. The biggest problem is that Python 2.7 is not available for the last
LTS, i.e. 10.04. To mitigate this, we decided to create a PPA containing
Python 2.7 and a bunch of packages that services such as Launchpad will need
to do their porting. This now exists, although it hasn't yet been tested with
any development branches of Launchpad or Landscape as far as I'm aware. If
you have your own data center porting task ahead of you, you can also use this
PPA, and if there are additional packages you need for 10.04, you can create
your own PPA which depends on ours, and build those extra packages there.
But that's all boring stuff. Let's have some fun!
The other decision we made concerns Python 3. I strongly feel that the Python
community is very close to …
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Update 2016-11-28: I've updated this article with new instructions!
sbuild is an excellent tool for locally building Ubuntu and Debian packages.
It fits into roughly the same problem space as the more popular pbuilder, but
for many reasons, I prefer sbuild. It's based on schroot to create chroot
environments for any distribution and version you might want. For example, I
have chroots for Ubuntu Oneiric, Natty, Maverick, and Lucid, Debian Sid,
Wheezy, and Squeeze, for both i386 and amd64. It uses an overlay filesystem
so you can easily set up the primary snapshot with whatever packages or
prerequisites you want, and the individual builds will create a new session
with an overlaid temporary filesystem on top of that, so the build results
will not affect your primary snapshot. sbuild can also be configured to save
the session depending on the success or failure of your build, which is
fantastic for debugging build failures. I've been told that Launchpad's build
farm uses a customized version of sbuild, and in my experience, if you can get
a package to build locally with sbuild, it will build fine in the main archive
or a PPA.
Right out of the box, sbuild will work great for individual package builds,
with very little configuration or setup. The Ubuntu Security Team's wiki
page has some excellent instructions for getting started (you can stop
reading when you get to UMT :).
One thing that sbuild doesn't do very well though, is help you build a stack
of packages. By that I mean, when you have a new package that itself has new
dependencies, you need to build those dependencies first, and then build your
new package based on those dependencies. Here's an example.
I'm working on bug 832864 and I wanted to see if I could build the …
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On Monday, I lost my home directory on my primary development machine. I'd
had this machine for a couple of years but it was still beefy enough to be an
excellent development box. I've upgraded it several times with each new
Ubuntu release, and it was running Natty. I had decent sbuild and pbuilder
environments, and a bunch of virtual machines for many different flavors of
OS.
I'd also encrypted my home directory when I did the initial install. Under
Ubuntu, this creates an ecryptfs and does some mount magic after you
successfully log in. It's as close to FileVault as you can get on Ubuntu,
and I think it does a pretty good job without incurring much noticeable
overhead. Plus, with today's Ubuntu desktop installers, enabling an encrypted
home directory is just a trivial checkbox away.
To protect your home directory, ecryptfs creates a random hex passphrase that
is used to decrypt the contents of your home directory. To protect this
passphrase, it encrypts it with your login password. ecryptfs stores this
"wrapped" passphrase on disk in the ~/.ecryptfs/wrapped-passphrase file.
When you log in, ecryptfs uses your login password to decrypt
wrapped-passphrase, and then uses the crazy long hex number inside it to
decrypt your real home directory. Usually, this works seamlessly and you
never really see the guts of what's going on. The problem of course is that
if you ever lose your wrapped-passphrase file, you're screwed because
without that long hex number, your home directory cannot be decrypted. Yay
for security, boo for robustness!
When you do your initial installation and choose to encrypt your home
directory, you will be prompted to write down the long hex number, i.e. your
unwrapped passphrase. Here's the moral of the story. 1) You should do
this; 2) You …
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So, yesterday (June 21, 2011), six talented and motivated Python hackers from
the Washington DC area met at Panera Bread in downtown Silver Spring,
Maryland to sprint on PEP 382. This is a Python Enhancement Proposal to
introduce a better way for handling namespace packages, and our intent is to
get this feature landed in Python 3.3. Here then is a summary, from my own
spotty notes and memory, of how the sprint went.
First, just a brief outline of what the PEP does. For more details please
read the PEP itself, or join the newly resurrected import-sig for more
discussions. The PEP has two main purposes. First, it fixes the problem of
which package owns a namespace's __init__.py file,
e.g. zope/__init__.py for all the Zope packages. In essence, it eliminate
the need for these by introducing a new variant of .pth files to define a
namespace package. Thus, the zope.interfaces package would own
zope/zope-interfaces.pth and the zope.components package would own
zope/zope-components.pth. The presence of either .pth file is enough
to define the namespace package. There's no ambiguity or collision with these
files the way there is for zope/__init__.py. This aspect will be very
beneficial for Debian and Ubuntu.
Second, the PEP defines the one official way of defining namespace packages,
rather than the multitude of ad-hoc ways currently in use. With the pre-PEP
382 way, it was easy to get the details subtly wrong, and unless all
subpackages cooperated correctly, the packages would be broken. Now, all you
do is put a * in the .pth file and you're done.
Sounds easy, right? Well, Python's import machinery is pretty complex, and
there are actually two parallel implementations of it in Python 3.3, so
gaining traction on …
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TL;DR: Ubuntu 12.04 LTS will contain only Python 2.7 and 3.2, while Ubuntu
11.10 will contain Python 3.2, 2.7 and possibly 2.6, but possibly not.
Last week, I attended the Ubuntu Developer Summit in Budapest, Hungary.
These semi-annual events are open to everyone, and hundreds of people
participate both in person and remotely. Budapest's was called UDS-O, where
the 'O' stands for Oneiric Ocelot, the code name for Ubuntu 11.10, which
will be released in October 2011. This is where we did the majority of
planning for what changes, new features, and other developments you'll find in
the next version of Ubuntu. UDS-P will be held at the end of the year in
Orlando, Florida and will cover the as yet unnamed 12.04 release, which will
be a Long Term Support release.
LTS releases are special, because we make longer guarantees for official
support: 3 years on the desktop and 5 years on the server. Because of this,
we're making decisions now to ensure that 12.04 LTS is a stable, confident
platform for years to come.
I attended many sessions, and there is a lot of exciting stuff coming, but I
want to talk in some detail about one area that I'm deeply involved in.
What's going to happen with Python for Oneiric and 12.04 LTS?
First, a brief summary of where we are today. Natty Narwhal is the code
name for Ubuntu 11.04, which was released back in April and is the most recent
stable release. It is not an LTS though; the last LTS was Ubuntu 10.04 Lucid
Lynx, release back in October 2010. In Lucid, the default Python
(i.e. /usr/bin/python) is 2.6 and Python 2.7 is not officially …
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