Microsoft gives MSDN Premium subscription to PSF members

This almost went through unnoticed. Steve Holden (Python Software Foundation) has worked out a fantastic deal with Sam Ramji and Tom Hanrahan (both leading Open Source guys at Microsoft). Microsoft has given fourteen MSDN Premium subscriptions to Python core developers and PSF members. I'm one of the lucky few. [1], [2]

The premium subscription includes licenses and downloads of almost every Microsoft product from MS-DOS 6.22 to Windows 7, all versions of Visual Studio and many more stuff. This is very useful for Python core developers. Every developer with a subscription can finally set up multiple virtual boxes with 32 and 64bit versions of XP, Vista and Windows 7 to test and debug issues. 64bit versions of Windows were hard and costly to come by.

I'll keep my Ubuntu boxes for daily work and I'll still be skeptical about Microsoft's open source politics. However I'm glad that their paradigm towards Open Source is changing into the right direction. Python (more precisely IronPython) is going to become more important to Microsoft. I'll put my subscription into good use.

Thanks to Sam, Tom and Steve!

[1] http://mail.python.org/pipermail/python-dev/2009-July/090704.html
[2] http://mail.python.org/pipermail/python-dev/2009-August/091020.html

How to add a new module search path

Once in a while Python users are asking how to add some directories to sys.path permanently. Usually a solution like the PYTHONPATH env variable are suggested to the op. Other solutions require root privileges or modify the search path for all users. PEP 370 adds another way that is more clean and easy to use. It doesn't require root privileges and it doesn't suffer from other issues. PYTHONPATH causes trouble for multiple Python versions. C extensions only work for one version of Python, most Python modules won't work on Python 2 and 3.

My preferred way adds additional search pathes just for one version of Python and just for me. It uses a .pth file as explained in the site module manual. .pth files only work in site-packages directories, either the global or the user specific directories.

The Python way

$ python2.6
>>> import os
>>> import site
>>> site.USER_SITE

'/home/heimes/.local/lib/python2.6/site-packages'

Create the directory if it doesn't exist yet

>>> if not os.path.isdir(site.USER_SITE):
... os.makedirs(site.USER_SITE)
...

mypath.pth is going to contain my list of addition search path

>>> mypth = os.path.join(site.USER_SITE, "mypath.pth")
>>> path_to_add = ["/home/heimes/modules", "/home/heimes/other_modules"]

Add a list of search paths line by line, also make sure we end with an empty line

>>> with open(mypth, "a") as f:
... f.write("\n".join(path_to_add))
... f.write("\n")
...
>>>

The bash way

$ python2.6 -m site --user-site
/home/heimes/.local/lib/python2.6/site-packages
$ mkdir -p $(python2.6 -m site --user-site)
$ echo "/home/heimes/more_modules" >> $(python2.6 -m site --user-site)/mypath.pth

Let's check if it works

check the pth file

$ cat $(python2.6 -m site --user-site)/mypath.pth
/home/heimes/modules
/home/heimes/other_modules
/home/heimes/more_modules

Let's see if the modules are in the new search path ... they aren't because the directories don't exist yet.

$ python2.6 -m site
sys.path = [
'/home/heimes',
'/usr/lib/python2.6',
'/usr/lib/python2.6/plat-linux2',
'/usr/lib/python2.6/lib-tk',
'/usr/lib/python2.6/lib-old',
'/usr/lib/python2.6/lib-dynload',
'/home/heimes/.local/lib/python2.6/site-packages',
'/usr/lib/python2.6/dist-packages',
'/usr/lib/python2.6/dist-packages/PIL',
'/usr/lib/python2.6/dist-packages/gst-0.10',
'/var/lib/python-support/python2.6',
'/usr/lib/python2.6/dist-packages/gtk-2.0',
'/var/lib/python-support/python2.6/gtk-2.0',
'/var/lib/python-support/python2.6/pyinotify',
'/usr/lib/python2.6/dist-packages/wx-2.6-gtk2-unicode',
'/usr/local/lib/python2.6/dist-packages',
]
USER_BASE: '/home/heimes/.local' (exists)
USER_SITE: '/home/heimes/.local/lib/python2.6/site-packages' (exists)
ENABLE_USER_SITE: True

create one example directory

$ mkdir /home/heimes/modules
$ python2.6 -m site
sys.path = [
'/home/heimes',
'/usr/lib/python2.6',
'/usr/lib/python2.6/plat-linux2',
'/usr/lib/python2.6/lib-tk',
'/usr/lib/python2.6/lib-old',
'/usr/lib/python2.6/lib-dynload',
'/home/heimes/.local/lib/python2.6/site-packages',
'/home/heimes/modules',
'/usr/lib/python2.6/dist-packages',
'/usr/lib/python2.6/dist-packages/PIL',
'/usr/lib/python2.6/dist-packages/gst-0.10',
'/var/lib/python-support/python2.6',
'/usr/lib/python2.6/dist-packages/gtk-2.0',
'/var/lib/python-support/python2.6/gtk-2.0',
'/var/lib/python-support/python2.6/pyinotify',
'/usr/lib/python2.6/dist-packages/wx-2.6-gtk2-unicode',
'/usr/local/lib/python2.6/dist-packages',
]
USER_BASE: '/home/heimes/.local' (exists)
USER_SITE: '/home/heimes/.local/lib/python2.6/site-packages' (exists)
ENABLE_USER_SITE: True

Easy, isnt' it?

libxml2 crash on 64bit Ubuntu

I've spent the last couple of hours debugging a really strange segfault. Our application stack had a reproduceable crash in libxml2 -- but only with self compiled versions of libxml2. Ubuntu's 2.6.32 worked like a charm, my self compiled 2.6.32 didn't. The very same version works on several other Debian, Redhat and SuSE boxes, 32 and 64bit, too. WTF!?

The crash always occured in xmlIO.c:__xmlParserInputBufferCreateFilename() with xmlGzfileOpen() as open handler. After several gdb debugging sessions and several recompiles I noticed a suspicious message in the make output:

xmlIO.c: In function 'xmlGzfileOpen_real':
xmlIO.c:1132: warning: implicit declaration of function 'gzopen64'
xmlIO.c:1132: warning: nested extern declaration of 'gzopen64'
xmlIO.c:1132: warning: assignment makes pointer from integer without a cast
xmlIO.c: In function 'xmlGzfileOpenW':
xmlIO.c:1200: warning: assignment makes pointer from integer without a cast

The message only occured during my own compiles but not during "apt-get source -b libxml2" . Apparently Ubuntu has patched the sources to fix the issue. The changelog contains yet another hint:

* libxml.h: define _LARGEFILE64_SOURCE to properly get gzopen64 defines in zlib.h. Closes: #439843. Thanks Dann Frazier.

That's the solution to my problem! CFLAGS="-D_LARGEFILE64_SOURCE" ./configure and both the compiler warning and the crash is gone.

multiprocessing 2.6.2.1 released

A new version of the multiprocessing backport to Python 2.4 and 2.5 has been released. It contains all fixes from the Python 2.6 branch. As usually the release is available as tar.gz and Windows installer for Python 2.4 and 2.5 on PyPI.

Python 3.0 is dead, long lives Python 3.0

Now it's official. The developer teams has decided against a Python 3.0.2 bugfix release [1]. Python 3.0 will not see another release and everybody should move to Python 3.1 as soon as possible. The 3.1 release is so much better than 3.0 and the list of incompatibilities is small. Have fun!

[1] Barry Warsaw, Python 3.0 (pinin' for the fjords)

Ubuntu 9.04 (Jaunty) and Python

Last week I've started with testing Ubuntu 9.04. The update process ran smoothly as usual but I had to switch from fglrx to radeonhd because the proprietary ATI driver seems to lack support for the graphics card of my Lenovo T60p. Well down ATI ...

Good news

Ubuntu 9.04 is shipped with four versions of Python:

• 2.4.6 (Zope2 still requires Python 2.4)
• 2.5.4
• 2.6.2 (default)
  
• 3.0.1

You can't ask for more Python versions!

Bad news

Ubuntu's Python team hasn't included my multiprocessing backport for Python 2.4 and 2.5 in Jaunty although Sandro Tosi has created a Debian package. You still have to install it manually from PyPI.

Warning

Did you install Python 2.6 yourself before? Make sure you remove it ASAP!

At first I couldn't figure out why lots of Python based applications were broken. It was a major issue for me because Ubuntu uses Python in lots of places. Then it occured to me that it may be related to my previous installation of Python 2.6. Ubuntu 8.04 didn't use Python 2.6 but 9.04 uses 2.6 as default Python for its apps. And /usr/local has precedence over /usr. Once it was gone everything worked again.

In order to wipe your own installation of Python from your hard disk you have to remove

• /usr/local/bin/py*2.6
• /usr/local/lib/libpython2.6.so*
• /usr/local/lib/python2.6 (except for an empty site-packages directory)

Have fun!