Alexandre Vassalotti

During this summer, I will post each week a short summary of what I did, the challenges I encountered and what I learned during my Summer of Code project. I am doing this for helping me to keep track of my progresses.

So how was my first week? It was great. I don’t know why but I love programming in C. It is just plain fun. I thought learning Python C API was going to be hard, but it is quite easy after all. I just read the code in Python itself and check the reference manual for the things I don’t know. My biggest surprise, this week, was really learning how to do subclassable types. It is strikingly easy, however it’s quite verbose. You can look at my scratch extension module, if you want a minimal working example.

Other than learning the C API, I started working on the cStringIO/StringIO merge. My current plan is to separate the cStringIO module into two private submodules, _bytes_io and _string_io. One will be for bytes literals (ASCII), and the other for Unicode. This will reflect the changes made to the I/O subsystem in Python 3000. These two submodules will provide optional implementations for the speed-critical methods, like .read() and .write().

One the best things, of this week, was the great feedback I got from other Python developers, and particularly from my mentor Brett Cannon, who cheerfully answers all my questions. Now, I just hope the following week will be as fun, or even more, as this one.

This is my first blog entry with my brand new toy, the weblogging mode for Emacs. It uses the XML-RPC interface of your favorite blogging platform to manage your blog. In other words, it transformes Emacs into a thermonuclear blog editor.

Even better, the installation is simple and easy. Here’s the instructions how to get it working. First, check out the source code of weblogger into your .emacs.d directory:

cd ~/.emacs.d/
cvs -z3 -d:pserver:anonymous@cvs.savannah.nongnu.org:/sources/emacsweblogs \
  co -d weblogger weblogger/lisp

Then, make Emacs load this mode on startup by adding these two lines to your .emacs configuration:

(add-to-list 'load-path "~/.emacs.d/weblogger")
(require 'weblogger)

Now, you probably want to reload your configuration with M-x eval-buffer (assuming your .emacs is still open). Finally, setup weblogger for your blog with M-x weblogger-setup-weblog. This command will ask you a few simple questions, like your username and password for your blog. It will also ask you for the location of the XML-RPC interface of your blog. If you’re using WordPress, it will be somewhere like http://example.com/blog/xmlrpc.php. If you’re using another blog publishing platform like Blogger or MovableType, it will be somewhere else, so check your documentation.

And you’re done! You can now start new a new post with M-x weblogger-start-entry. Weblogger also includes a whole set of other commands for managing your blog. Look them up, with C-h a weblogger RET. Happy blogging!

• AMD is announcing plans to deliver open graphics drivers, at Red Hat Summit.
• Dell to offer Ubuntu on some of their machines, in the United States.
• Intel partners with Ubuntu to create an open source platform for mobile devices.
• Sun Microsystems completes the release of Java under the GPLv2.

Quick hack: here a script for Greasemonkey that changes the default proportional font to fixed font on Gmail. I was tired reading distorted PEP, and code patches. And since Gmail doesn’t allow changing the font style, I had to write this simple script. Enjoy!

Today, there will be a special quiz on Python hosted by me, in #ubuntu-trivia on FreeNode, at 20:00 UTC. Most of the quiz will be to write some simple procedures, faster than your opponents. The winner will, of course, get a superb prize — 5 Ubuntu stickers! Obviously, the real prize is the fun that will get during the quiz. And who knows, maybe you will learn a few neat tricks. So, see you there!

Yesterday, I was reading Peter Norvig’s excellent article about spell checking. Then, I started to look to some of his older stuff. So, I found his Python IAQ (Infrequently Answered Questions), and discovered a pretty neat trick:

h = [None]  # history

class Prompt:
    """A prompt a history mechanism.
    From http://www.norvig.com/python-iaq.html
    """
    def __init__(self, prompt='h[%d] >>> '):
        self.prompt = prompt

    def __str__(self):
        try:
            if _ not in h: h.append(_)
        except NameError:
            pass
        return self.prompt % len(h)

    def __radd__(self, other):
        return str(other) + str(self)

sys.ps1 = Prompt()
sys.ps2 = '     ... '

This improve the interactive prompt of Python with a shell-like history mechanism. With this prompt, you can reuse any previous value returned by Python. For example:

h[1] >>> lambda x: x * 2
<function <lambda> at 0xb7dab41c>
h[2] >>> [1, 2, 3, 4, 5]
[1, 2, 3, 4, 5]
h[3] >>> map(h[1], h[2])
[2, 4, 6, 8, 10]

You can make it your default prompt, by adding the above in your .pythonrc.py. You will need to specify its location to Python with the environment variable PYTHONSTARTUP. Just add something like the following to your shell configuration (e.g., .bashrc or .zshrc).

export PTHONSTARTUP="$HOME/.pythonrc.py"

I am sure there is a ton of other useful modifications, which can be done with the startup file of Python. If you’re interested, here my brand new startup file. And if you know any other cool tricks for Python, please tell me!

If you are using a platform other than a i386, you will need to compile my Emacs packages yourself. So, here a simple guide how to do this.

1. First, make sure you have the source repository enabled, by adding deb-src http://ppa.launchpad.net/avassalotti/ubuntu gutsy main to your /etc/apt/sources.list.
2. Install the build-dependencies and some packaging tools:

   sudo apt-get update
   sudo apt-get build-dep emacs-snapshot
   sudo apt-get install dpkg-dev devscripts fakeroot emacsen-common

3. Download the source package and compile it with:

   fakeroot apt-get --compile source emacs-snapshot

4. Finally, install the newly built packages:

   sudo dpkg -i emacs-snapshot*.deb

Note, this final step may fail if you have an older version of the package already installed. If it is the case, just do it again.

Dear Applicant, Congratulations! This email is being sent to inform you that your application was accepted to take part in the Summer of Code.

Today, I am truly happy. I wasn’t expecting to be accepted, really, and perhaps no other candidate did. My accepted project is to merge C and Python implementations of the same interface (i.e., StringIO/cStringIO, Pickle/cPickle, etc), and my mentor is the Python star developer, Brett Cannon. This will be a challenging project; I will have to work hard and efficiently to be successful. But one thing is sure, I will have some great fun.

I would like to congrats everyone who have been accepted. A special thanks to students who will be working on Ubuntu, this summer. There is surely some great projects for Ubuntu. And also, another special thanks to the mentors, who will be helping us this summer.

As some of you may already know, I am a die-hard fan of productive editing. That is probably because I don’t find myself very fast, on a keyboard. So, I am always trying to find ways to improve my editing speed. And when I ain’t surfing on the web, I am either typing stuff in my shell or my editor. So today, I would like to share a few tricks I uses in my default shell, Z Shell.

The shell history can be a powerful tool. If you find yourself typing commands again, and again, and again, you probably can use it at your advantage. You probably already know about Ctrl+R, which is bound to history-incremental-search-backward command in most shells. Personally, I don’t find it very useful since it tries to find a match everywhere, but it’s better than cycling through the history with the Up/Down keys. In fact, anything is better than the Up/Down keys. So, why not rebind them to something more useful, like history-search-backward? Well, that is easy. With Zsh, you need to add these two line to your .zshrc:

bindkey '\e[A' history-search-backward
bindkey '\e[B' history-search-forward

In fact, if you’re using Emacs key-bindings, you don’t even need to do anything, because Meta+P and Meta+N are already bound to these two functions. Incidentally, Steven Harms is advocating to enable this feature by default in Ubuntu, for Bash’s users. Personally, I am not sure if it’s really necessary to make it a default. I am not a fan of modifications in .inputrc, either. But, I will leave that discussion for another blog post.

Now, that we have functional Up/Down arrow keys, can we do more? Yes, we can! Let me introduce one of my favorite features of Zsh, preemptive auto-completion. If you’re tired typing TAB a zillion times a day, you will love this one. This feature implements predictive typing using history search and auto-completion. Again, to enable it, just copy these lines to your configuration file:

autoload predict-on
zle -N predict-on
zle -N predict-off
bindkey '^Z'   predict-on
bindkey '^X^Z' predict-off
zstyle ':predict' verbose true

Here, note that predict-on and predict-off, are bounded to Ctrl+Z and Ctrl+X Z respectively. That means you can turn it on/off, whenever you need to. You will find useful to turn it off when you edit the middle of a command, since it can confuse the prediction. But other than that, it’s great.

Sometime, the shell editor is not enough for me — I need something more powerful when I edit long commands. So, I use another cool built in function of Zsh, called edit-command-line. With this feature, I can edit the current command with an external editor, defined by the environment variable $EDITOR. To enable it, just copy-and-paste this:

autoload edit-command-line
zle -N edit-command-line
bindkey '^Xe' edit-command-line

So, when I think the command will be long, like a for-loop. I just press Ctrl+X e, which launches, on my system, emacsclient. I am always running Emacs with its server, therefore the shell command is instantaneously loaded into a Emacs buffer. Then when I am done, I close the Emacs session with Ctrl+x # and the command appears in my shell. It is just sweet.

Even if you’re a master with your editor, nothing beats a short alias, or a shell script. I keep a full directory of useful scripts, to automate my daily tasks. At first, writing scripts feels a bit awkward. If you’re like me, you will always worry that your scripts might go terribly wrong, and eat your data. That’s totally normal, but don’t be a fool. Automating your tasks, even the most trivial ones, will save some of your precious time. Unlike scripts, which can really do some heavy automation, aliases are just a shell convenience, like auto-completion. Personally, I am not a big fan of fancy aliases. (I tend to use functions for the more fancy things.) Anyway, here some of my favourite aliases:

# Set up aliases
alias c=clear
alias d='dirs -v'
alias e=$EDITOR
alias grep=egrep
alias h=history
alias j=jobs
alias po=popd
alias pu=pushd
alias ss='screen -Rx'

# Global aliases -- These do not have to be
# at the beginning of the command line.
alias -g M='|more'
alias -g L='|less'
alias -g H='|head'
alias -g T='|tail'

# Go to parent directories without `cd'
setopt autocd
alias -g ...='../..'
alias -g ....='../../..'
alias -g .....='../../../..'

I certainly have a ton of shell tricks, but I will keep them for my other blog posts. So, that’s all folks!

A burned video, a zapped hard drive and a corrupt RAM module later , I have now, finally, got my system running again (and no, my computer was not struck by a lightning).

For the fans of my Emacs package, I just uploaded a new release, and I will continue to provide weekly releases. Unfortunately, it seems, due to a licensing issue, Romain Francoise orphaned emacs-snapshot and its related packages. Therefore, this means I will have to work harder and fix packaging bugs myself, instead of relying on his bug fixes.

A week before I lost my system, I had promised a special Python quiz, in the issue #31 of Ubuntu Weekly News. I have not forgotten my promise. So if you’re one of the lovers my twisted Ubuntu quizzes, get ready for an awesome quiz. Date and time, when the quiz will be held, will be announced, as usual, in the #ubuntu-trivia channel on FreeNode.

On the final note, I would like to mention that will start posting more frequently on my blog. My current roadmap includes some cool tips-and-tricks, fun script recipes, more stuff about Ubuntu. So, stay tuned!