Kiwi PyCon Sponsorship Drive

 Kiwi PyCon is approaching! You probably think that's a good thing, but if you're one of the poor volunteer organisers, that's a scary thought. Why? We have bills to pay, and very little income. That means it's time to shill for some cash! Below is an excerpt from our public sponsorship announcement email. If your company is willing to sponsor a good cause, please get in touch with me.

Kiwi PyCon is organised by the New Zealand Python User group - a not-for-profit organisation. We don’t make any profit from the conference, and the organisers donate their free time to make the event a success. We rely entirely on companies’ sponsorship to pay the bills.

Sponsorship has several advantages for you:

• It’s an opportunity to get brand exposure in front of the foremost Python experts from New Zealand and around the world.

• Presents a fantastic networking opportunity if you are looking to employ engineers now, or in the future.

• Align yourself with market leaders and past sponsors such as Github, Weta Digital, Catalyst IT, Mozilla. Become known as a Python promoter and industry leader. 

• Gold sponsors receive five complimentary tickets to the conference and their logo on the conference shirt and all print materials.

If you’d like to sponsor the conference, a document describing sponsorship opportunities is available here.

To get in touch, email kiwipycon-sponsorship@nzpug.org.

Python GObject Introspection oddness

I recently ported indicator-jenkins to Gtk3 using the python GObject Introspection Repository (gir) bindings. Ted Gould did most of the work, I just cleaned some bits up and made sure everything worked. One issue that puzzled me for a while is that the GObject library changed the way it's "notify" signal works between GObject 2 and GObject 3. I've not seen any documentation of this change, so I'll describe it here.

For this example, let's make a very simple class that has a single property:

import gobject

class MyClass(gobject.GObject):
    prop = gobject.property(type=int)

...and a very simple callback function that we want to call whenever the value of 'prop' changes:

def cb(sender, prop):
    print "property '%s' changed on %r." % (prop.name, sender)

Finally, with GObject 2 we can create an instance of 'MyClass' and connect to the 'notify' signal like this:

inst = MyClass()
inst.connect("notify", cb)
inst.prop = 42

When we run this simple program we get the following output:
property 'prop' changed on .
... which is what we expected. However, if we port this code to GObject 3, it should look like this:

from gi.repository import GObject

class MyClass(GObject.GObject):
    prop = GObject.property(type=int)


def cb(sender, prop):
    print "property '%s' changed on %r." % (prop.name, sender)


inst = MyClass()
inst.connect("notify", cb)
inst.prop = 42

However, running this gives an error:

/usr/lib/python2.7/dist-packages/gi/_gobject/propertyhelper.py:171: Warning: g_value_get_object: assertion `G_VALUE_HOLDS_OBJECT (value)' failed
  instance.set_property(self.name, value)
Traceback (most recent call last):
  File "gobject3.py", line 8, in cb
    print "property '%s' changed on %r." % (prop.name, sender)
AttributeError: 'NoneType' object has no attribute 'name'

The 'prop' parameter in the callback is set to None.

There is a solution however - connecting the callback to a more specific notification signal works as expected:

from gi.repository import GObject

class MyClass(GObject.GObject):
    prop = GObject.property(type=int)


def cb(sender, prop):
    print "property '%s' changed on %r." % (prop.name, sender)


inst = MyClass()
inst.connect("notify::prop", cb)
inst.prop = 42

 It took me a while to figure this out - hopefully I've saved someone else that work.

Indicator-jenkins is now even more awesome

My latest hobby project, indicator-jenkins is now even better (I wrote about this previously, in case you missed it).

New features since my last blog post:

• The code is now much nicer, and will be much easier to extend. My long-term goal is to support other types of CI servers (I'll probably have to change the project name I guess).
• Desktop notifications are generated for each new build of a monitored project. The notification includes the status and health report of the last build.
• LOTS of bug-fixes, especially around the settings UI. I'm still not happy with the settings dialog UI, but it's at least usable now.

To get it installed, do the following:

$ sudo add-apt-repository ppa:thomir/indicator-jenkins

$ sudo apt-get install indicator-jenkins

Then launch indicator-jenkins from the unity dash or command line (Note: Launching it from the command line generates a LOT of debug output - I will turn this off in future releases).

How to Compile Unity from Source

These instructions will help you build unity from source. However, there are a
few things to consider:

• I recommend that you never copy anything you've built locally outside your home directory. Doing so is asking for trouble, especially as we're building the entire desktop shell. If you manage to ruin your system-wide desktop shell you'll be a very sad programmer!
• I'm assuming that you're running the precise Ubuntu release (still in alpha at the time of writing, but very usable).
• I'm also assuming that you want to build unity from trunk (that is, lp:unity).

Without further ado, let's get to it:

Getting the source code

If you don't already have Bazaar installed, install it now:

sudo apt-get install bzr

You may want to make yourself a folder for the unity code. I tend to do something like this:

mkdir -p ~/code/unity
cd ~/code/unity

Let's grab the code from launchpad:

bzr branch lp:unity trunk

This may take a while. If you prefer to use Bazaar checkouts instead of branches, that's fine to.

Installing Build Dependancies

We need to get the build-dependancies for unity. Thankfully, apt-get makes this trivial:

sudo apt-get build-dep unity

Compiling Unity

I have a set of bash functions that makes this step significantly easier. To use them, copy the following bash code into a file in your home directory called ".bash_functions":

function recreate-build-dir()
{
   rm -r build
   mkdir build
   cd build
}

function remake-autogen-project()
{
    ./autogen.sh --prefix=/home/thomi/staging --enable-debug
    make clean && make && make install
}

function remake-unity()
{
    recreate-build-dir
    cmake .. -DCMAKE_BUILD_TYPE=Debug -DCOMPIZ_PLUGIN_INSTALL_TYPE=local -DCMAKE_INSTALL_PREFIX=/home/thomi/staging/ -DGSETTINGS_LOCALINSTALL=ON
    make  && make install
}

function unity-env
{
 export PATH=~/staging/bin:$PATH
 export XDG_DATA_DIRS=~/.config/compiz-1/gsettings/schemas:~/staging/share:/usr/share:/usr/local/share
 export LD_LIBRARY_PATH=~/staging/lib:${LD_LIBRARY_PATH}
 export LD_RUN_PATH=~/staging/lib:${LD_RUN_PATH}
 export PKG_CONFIG_PATH=~/staging/lib/pkgconfig:${PKG_CONFIG_PATH}
 export PYTHONPATH=~/staging/lib/python2.7/site-packages:$PYTHONPATH
}

Note: You will need to replace all instances of "/home/thomi" with your own home directory path!

Now run this in a terminal:

echo ". ~/.bash_functions" >> ~/.bashrc

This ensures that the next time you open a bash shell the functions listed above will be available to you. To avoid having to close and re-open a terminal, we can read them manually just this once:

. ~/.bash_functions

You should now be able to run:

remake-unity

from the trunk/ directory we created earlier. That's it - you're building unity!

Not so Fast!

Chances are, while trying to build unity, you found that it needed a newer version of one of the several supporting projects than you had installed. At the time of writing, you can't compile unity without first building nux from sources first. Thankfully, that's pretty easy with the use of the functions you now have set up.
First we get the source code:

mkdir -p ~/code/nux
cd ~/code/nux
bzr branch lp:nux trunk
cd trunk

Then we need to get the build dependencies for nux.

sudo apt-get build-dep nux

Unfortunately there are a fewpackages missing, so you'll want to install them as well:

sudo apt-get install gnome-common libibus-1.0-dev libgtest-dev google-mock libxtst-dev

Then we use the functions above to build nux:

remake-autogen-project

That's it! You can then go back and build unity - hopefully this time with better success.

Build Notes

You may have noticed that the remake-* scripts do a complete rebuild every time. If you'd prefer to just build the files that have changed since last time, change to the trunk/build/ directory, and run:

make && make install

Running Unity

If you'd like to run the version of unity you've built, rather than the system-wide version, open a terminal and run the following commands:

unity-env
unity --replace &

The first line patches several environment variables such that unity will subsequently be launched from your local staging directory. These environment variables will remain changed until you close the terminal, so you need only run unity-env once.

Introducing: indicator-jenkins

For my day job I've been monitoring a jenkins instance (specifically, the public Ubuntu QA jenkins instance) using my web browser. This is obviously suboptimal - I'd like to be able to see the state of the jenkins jobs I'm interested at a glance, without having to open my web browser.

I couldn't find a solution to my problem, so I created one: indicator-jenkins is a panel indicator for your desktop manager of choice. It allows you to select one or more jobs from a jenkins server, and follow the job state without having to open your browser.

The project is hosted on launchpad, and is built daily into my PPA. To install it (I'm assuming you're running Ubuntu):

$ sudo add-apt-repository ppa:thomir/indicator-jenkins

$ sudo apt-get update

$ sudo apt-get install indicator-jenkins

Once it's installed you can launch it in a couple of different ways:

• From a terminal - jut run indicator-jenkins. If you run it on the terminal you'll get a lot of debugging output (useful if you want to submit a patch, or figure out why it's not working).
• From the unity dash - open the dash, and search for 'jenkins' - it's probably going to be the first link.
  
  

Once it's running you should see the jenkins icon in your panel. To set it up, click the icon to open the settings dialog, enter the URL of the jenkins instance you want to look at, hit the refresh button, and pick the job(s) you want to monitor. Click OK and you're done! It's simpler than it sounds - see for yourself:

Right now it's pretty rough-and-ready - there are many features I'd like to add:

• Integrate desktop notifications, so you can be alerted when a job state changes.
• Customise panel icon based on job state (i.e.- show a red icon if any of the monitored jobs are failing).
• Allow user to customise refresh period.
• Allow user to monitor jobs from more than one jenkins server.
• Show more information about a jenkins job. For a start, show stability as well as current status, and maybe in the future show unity test pass/failure rates for projects that have that information.

How it's Made:

The entire application is written in python. We make use of several python modules:

• The python-appindicator package gives us the ability to create an icon on the menu, and the python gtk2 bindings are used to create the menu and settings dialog.
• The python 'multiprocessing' module is used to spin up worker processes to fetch the data from jenkins. Initially the application used threads for this, but python's threading support isn't great, and it was taking too long. 
• The python 'json' module is used to save and load settings.
• The python-jenkins package is used to communicate with the jenkins server.

This is a great example of python's "batteries included" approach to programming. All you have to do is provide the glue between already-existing python modules.

KiwiPyCon Sloecode Talk

It's about time I posted my Kiwi PyCon talk from last August! I spent an enjoyable 30 minutes talking about what Sloecode is, how we built it, and the problems encountered along the way. As per my usual approach to public speaking, I tried to keep things light-hearted and entertaining. Anyway, the slides and audio are available here:

Introducing Sloecode: a python-powered, installable code-forge.

View another webinar from ThomiRichards

Dear Journalists: Bits and Bytes

Dear Journalist type person,

There's something we must discuss. You see, you've been making a very basic mistake in many of your articles when it comes to writing about the Internet, and specifically Internet speeds. Let's take a look at a small quote:

...unless you have an internet connection of impossible speeds. (Mine is nominally 10MB, by the way, which in practice means maximum download speeds of 1.4 megabytes per second).

(source: Rock-Paper-Shotgun).

Can you spot the problem here? Internet speeds are measured in megabits per second. The symbol for 'bits' is a lower-case 'b', so an Internet connection that's 10 Megabits per second could be written as "10 Mbps". I guess if you're feeling lazy you could leave off the "ps", and end up with "10 Mb" (although it's a really sloppy thing to do), but NEVER "10 MB" - that means something else entirely.

Modern PCs use bytes that contain 8 bits. The correct symbol for a byte is an upper-case 'B'. so "10 MB" means "ten mega-bytes", not mega-bits, which is probably what you meant when you were describing the speed of your Internet connection.

Back to our Internet connection that runs at 10Mbps. It's unfortunate that speeds are measured in bits, because a much more useful measure is bytes per second, since that's how we deal with data sizes. We know that a CD ISO image is likely to be around 700 MB, an MP3 file around 3 MB, and an image from a digital camera to be around 1 MB. To convert our 10Mbps connection speed to megabytes per second, we divide by 8, and get 1.25MBps. However, this is the theoretical maximum speed, and there's a lot of overhead in any network connection, so in practise it's unlikely you will experience anything close to this maximum speed.

If your eyes glazed over, or perheps you felt light-headed reading that, here are a few take-home points to make it easier for you:

• Connection speeds are measured in megabits-per-second. The correct unit symbol for this is "Mbps".
• Files are measured in Megabytes.
• A Byte has 8 bits. So to turn your connection speed into something useful, divide the number by 8 and make the unit symbol "MBps".

I would be honoured if you'd consider this small point next time you go to write online. Some of us are acutely sensitive to these matters, and you really don't want to upset the geeks of this world.

Kind Regards,