Yoan Blanc’s weblog

Yesterday night, a friend of mine and I discussed how to know how many glasses are touching each other when you says “Cheers!” before drinking.

It’s a simple combinaison written like that like you learn it at school. p is 2 and n is the number of friends you have (you included).

But for this simple example where p is set to 2, this big equation with lots of ! inside it, can be written like a sum.

But a sum isn’t very friendly to a computer. It’s not bad but you can do this better. My solution abuse of the modulo function.

It’s probably clearer in Python.

cheers = lambda x: (x/2) * (x-(x+1)%2)

You’ll discover some cool things like :

10 → 45
100 → 4950
1,000 → 499,500
1,0000 → 49,995,000

or

20 → 190
200 → 19,900
2,000 → 1,999,000
2,0000 → 199,990,000

Have fun!

cheers = lambda x: (x/2) * (x-(x+1)%2)

At my work, we just installed a development server that will host the demo of the work of the web developers. I’ll explain here how I managed to do that.

First of all, install your box. I choose Ubuntu server my employer loves everything that is trendy. If I prefer Gentoo, Ubuntu is probably more convenient for most users.

The power of Ubuntu Server is that you can directly install a LAMP server. Here we’ll need some extra packages for Trac and Subversion.

sudo apt-get install trac libapache2-svn libapache2-mod-python

The idea is to have for a project a virtual host, a Subversion repository and a Trac.

I’ve choose this directory structure:

~/projects/
   .htpasswd        (Password file)
   project_name/
      apache.conf   (Apache configuration file)
      log/          (Apache logs)
      svn/          (Subversion repository)
      trac/         (Trac)
      www/          (VirtualHost document root)
		

For the better flexibility and don’t deal with a DNS server. Every project will be mapped on a port.

Here is a Python script that will create for you this structure.

All you need is to create the directory projects and .htpasswd in it, then run :

python create_project.py project_name port

An example:

1. Create your project called “test” and mapped on the port 8000.

   python create_project.py test 8000

2. Install it in Apache.

   sudo ln -s /home/`whoami`/projects/test/apache.conf /etc/apache2/sites-enabled/test

3. Restart Apache to see the change

   sudo /etc/init.d/apache2 restart

4. Open you browser and visit:

   • http://your-server-ip:8000/
   • http://your-server-ip/svn/test/
   • http://your-server-ip/trac/test/

For a very convenient server, I suggest you to use ssh for everybody. They just have to give you their public key, you add it into .ssh/authorized_keys and then they can log in safely for SCP, SFTP (need to configure the FTP server) or remote control.

Feel free to give me feedback about your experience, this script is in a early stage of development use it at your own risk.

After having discovered that PHP sucks less than JavaScript reading the feedback of the last WebTuesday (I’ll need to go there one day, a Tuesday maybe). Harry mentioned in his presentation Selenium a powerful tool for doing Web Application Unit Testing. Sounds great! Let’s dive!

1. Download it: Selenium Remote Control

2. Unzip it and go in.

3. Run the server (Java is required).

   cd server/
   java -jar selenium-server.jar -interactive

4. We’ll try it with Python but Selenium support lots of cool languages like Ruby, Perl, Java and .Net (try Mono).

   In an other shell go into the selenium directory and then into the python dir.

   Simply run:

   python test_google.py

   Rocks? Fails? For myself, it fails with firefox but I manage to run it with Opera.

5. Too Fast? Let’s try it into the Python shell. From the python directory run:

   python

   Woo! I hope you already done that before, you may love it.

   from selenium import selenium
   sel = selenium('localhost', 4444, '*opera', 'http://www.google.ch')
   sel.start()

   Wait a second, it runs Opera for you.

   sel.open('http://www.google.ch')
   sel.type('q', 'Yoan Blanc')
   sel.click('btnG')
   print sel.get_title()

   It normally displays: “u'Yoan Blanc - Recherche Google'”. Now you can quit.

   sel.stop()

   Hit Ctrl+D to quit the Python shell

Selenium will become your next new friend (after Firebug of course) for testing your web application.

A friend of mine, who loves C# and gonna play with Python, asked me about the file hierarchy of the pythonic module/package. For every Java or C# users it’s a bit different.

In the beautiful world of Java, a file is a class. Everything is clean and at it’s own place. The file hierarchy reflects the package hierachy. It can be the jungle in the directories.

package/Foo.java      import package
package/bar/Bar.java  import package.bar
		

With C#, which is very (very) similar to Java, the one class per file is the usual way to do, but you aren’t forced to. And the hierarchy is also the namespace hierarchy (or not). In the example bellow the both files can be in completely different namespace, strange isn’t it?

package/file.cs     using Package
package/file2.cs    using Package.Foo.Bar

With Python, it’s much more fun because a directory is a package if it contains a __init__.py file. You can use this packages with use directory. .py files in it are modules, you can use them with use directory.file (without the extention). A module (a file) can contains lots of variables, functions and classes. For every Java/C# coder it’s very messy.

package/__init__.py     use package
package/module.py       use package.module
package/foo/__init__.py use package.foo
package/foo/bar.py      use package.foo.bar

I don’t think this is messy, this is flexible. You can arrange thing exactly how you will use them.

I’ve written a very messy implementation of the State Pattern in both C# and Python just for the fun. C# is full of public, private, abstract, override... but in Python you need (if you want) to check the type of the data you receive. (I definitely love Python but, you can do a very similar job in both languages). Oh, there is no documentation because it’s very basic (google around about this design pattern if you want).

For the curious, I’ll stay in Switzerland for a while. The Dublin offices will not hire me (for the moment, keep believing).

OpenID is a tool that allow you to login into several web applications with the same login. A light-weight decentralized authentication system.

If you can have one like me at my OpenID, you can also have your own, like, for example http://yoan.dosimple.ch/. What a nice idea.

Scott Kevton gives in his blog a status of the OpenID Bounty Program that support softwares like (PhpBB, MediaWiki, ...) to implement that feature.

Yesterday in the evening, I’ve watched a very interesting movie that will make you feel very powerless if you imagine having a talk with this kind of guy.

I hate that (fixing computer) and I know why, but I’m sometimes too gentle to refuse. Just because when you start, you never end. Always a phone call asking you to help them.

This time it’s for wifi troubles: installing a wifi access point or fixing another one. If people pay me, I’m doing that for the money not for my pleasure of helping a friend. And here is the main problem.

I’m doing things for my pleasure, it’s sometimes my pleasure to help, or giving some hints that can help people but I think that one day boys-and-girls-with-computer(s)-at-home need to care a little about how all this world works.

By fixing bugs you learns a lot! I learned a lot of things by running an unstable gentoo box. Once a month it breaks and you need to browse the bugzilla, forums, chat on IRC and so one. Just do thing by yourself.

I’m back from a little two-days trip over Dublin (mostly for a job). Show the Pictures I’ve made.

I’va nothing to say at the moment because I’m waiting for a feedback. Keep waiting (and believing)!