YUM error on CentOS 5

I have a VPS running CentOS 5 and I was always running yum to update its software. This went ok until few days ago when “yum update” brought this :

There was a problem importing one of the Python modules
required to run yum. The error leading to this problem was:

No module named cElementTree

Please install a package which provides this module, or
verify that the module is installed correctly.

It’s possible that the above module doesn’t match the
current version of Python, which is:
~~~~~~

If you cannot solve this problem yourself, please go to
the yum faq at:

http://wiki.linux.duke.edu/YumFaq

After around an hour I saw that an easy fix for the Python issue required gcc installed .. but it wasn’t installed so I searched for another solution, even simpler :

wget http://archives.fedoraproject.org/pub/archive/fedora/linux/core/6/i386/os/Fedora/RPMS/python-elementtree-1.2.6-5.i386.rpm

rpm -Uvh –oldpackage python-elementtree-1.2.6-5.i386.rpm

That fixed it! (the first thing to run was yum install gcc)

Hope this will help someone

Best wishes

Sorin

Posted in Linux Tips & Tricks.

1 comment

By Trimbitas Sorin – May 27, 2010

Cellular Automata – Conway’s Game of Life in HTML 5

I had to do a school project involving automata so, after searching what this means .. I came to “cellular automaton” and then to the “Conway’s Game of Life” on wikipedia. I remember doing such a project on RentACoder few years ago in Visual Basic but I didn’t knew this fancy name for it … “cellular automata”

The rules are pretty simple :

A cell with 0 or 1 neighbor dies because of underpopulation
A cell with 4 or more neighbors dies because of overpopulation
If an empty space has exactly 3 cells then a new cell is born in that empty space
If none of the above rules apply then the space does not change (a live cell remanins alive, and an empty space is still empty)

For implementing it .. I choosed the canvas object from HTML 5 specs as I wanted to learn a little bit about it.

The first step was writing the canvas tags with a default message in case the user’s browser does not support it.

HTML [Show Styled Code]:

HTML [Show Plain Code]:

<canvas id="drawBoard" width="400" height="400">
Your browser does not support canvas.
</canvas> 

After this .. came the fun part .. javascript

The code below is pretty simple :

We declare how many cells we want on the X/Y axes, how many pixels wide should be a cell and the delay between drawing the next generation of cells
We create 2 arrays, one for storing the initial colony and one for the next generation
We randomly fill with live cells the initial colony
We draw the initial colony and then we process the colony using the game’s rules

JAVASCRIPT [Show Styled Code]:

JAVASCRIPT [Show Plain Code]:

<script language="javascript">
// Settings
var x = 160; // How many cells on the X axis
var y = 140; // How many cells on the Y axis
var pixels_per_value = 4; // How many pixels wide should be a cell
var delay_between_frames = 400;// In ms
 
 
// Calculate the canvas width and height
var canvas_x = x * pixels_per_value;
var canvas_y = y * pixels_per_value;
 
// Create our matrix
var matrix = new Array(y);
var matrix_tmp = new Array(y);
for (i = 0; i < y; i++)
{
        matrix[i] = new Array(x);
        matrix_tmp[i] = new Array(x);
}
 
// Fill with some random points
var random = 1600;
var m,n;
for (i = 0; i < random; i++)
{
        m = Math.floor(Math.random()*y);
        n = Math.floor(Math.random()*x);
        matrix[m][n] = 1;
}
 
// Get the canvas reference and the 2D context
var canvas = document.getElementById('drawBoard');
// Set canvas size
canvas.width = canvas_x;
canvas.height = canvas_y;
var context = canvas.getContext('2d');
 
// Draw the first cell generation
draw_matrix();
 
// Call for the next generation of the cell colony
setTimeout("process_life()", delay_between_frames);
 
 
function process_life()
{
        var neighbours = 0;
        matrix_tmp = matrix.clone();
        for (i = 0; i < y; i++)
        {
                for (j = 0; j < x; j++)
                {
                        neighbours = count_neighbours(i,j);
                        // Underpopulation
                        if (neighbours < 2)
                        {
                                matrix_tmp[i][j] = 0;
                        }
                        // Overcrowding
                        if (neighbours > 3)
                        {
                                matrix_tmp[i][j] = 0;
                        }
                        // Birth
                        if (neighbours == 3)
                        {
                                matrix_tmp[i][j] = 1;
                        }
                }
        }
        matrix = matrix_tmp.clone();
        draw_matrix();
        setTimeout("process_life()", delay_between_frames);
}
 
// Added so we can copy the array between steps
Array.prototype.clone = function ()
{
        var tmp = new Array(); 
        for (var property in this) 
        {
                tmp[property] = typeof (this[property]) == 'object'  ? this[property].clone() : this[property];
        } 
        return tmp;
}
 
 
function count_neighbours(i, j)
{
        var count = 0;
        // Check for its maximum 8 neighbours
        if (matrix[i][j-1] == 1) count++;
        if (matrix[i][j+1] == 1) count++;
        //
        if (matrix[i-1] != undefined)
        {
                if (matrix[i-1][j] == 1) count++;
                if (matrix[i-1][j-1] == 1) count++;
                if (matrix[i-1][j+1] == 1) count++;
        }
        if (matrix[i+1] != undefined)
        {
                if (matrix[i+1][j] == 1) count++;
                if (matrix[i+1][j-1] == 1) count++;
                if (matrix[i+1][j+1] == 1) count++;
        }
        return count;
}
 
function draw_matrix()
{
        for (i = 0; i < y; i++)
        {
                for (j = 0; j < x; j++)
                {
                        draw_matrix_point(j, i, matrix[i][j]);
                }
        }
}
 
 
function draw_matrix_point(i, j, status)
{
        var origin_x = i * pixels_per_value;
        var origin_y = j * pixels_per_value;
        if (status == 1)
        {
                context.fillStyle = '#00FF00';
        }
        else
        {
                context.fillStyle = '#FF0000';
        }
        draw_rectangle(context, origin_x, origin_y, pixels_per_value, pixels_per_value);
}
 
// Draw a rectangle based on x/y origin point and having a specified width and height
function draw_rectangle(context, origin_x, origin_y, width, height)
{
        context.beginPath();
        context.rect(origin_x, origin_y, width, height);
        context.closePath();
        context.fill();
}
</script> 