Archive for April, 2007

Smoked brains for dinner

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!

Boosted Python Startup

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!

Pretty Emacs: Compile guide for unsupported platforms

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.

Flipping bits this summer

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.

Welcome to Mr. Crystal Ball

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!

Back in Business

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!