Funny Quote of the Day

- Thomas A. Edison - "To invent, you need a good imagination and a pile of junk."

Wisdom of the day

"Logic is the art of going wrong with confidence." -Joseph Wood Krutch

How to know what version of ubuntu you are running

To Know what is the version of ubuntu you are running just run the following command:

sudo cat /etc/lsb-release

your output should be somethinglike that:

DISTRIB_ID=Ubuntu
DISTRIB_RELEASE=$version
DISTRIB_CODENAME=$codename
DISTRIB_DESCRIPTION=$description


thats it, peace of cake ha...

How to disable the your linux firewall(iptables)

Lately i have a new fedora box at work and i was working in a demo project so that i wanted to run a local mercurial server so that my colleagues and myself can use it to work on our demo project.

I tried the hg serve command and it worked but only locally on my machine and it didnt work with any of my local network machines, so i found out that my firewall(iptables) is on and a colleague helped me to turn if off, here is the How ?

sudo service iptables stop
sudo iptables -F
sudo service iptables save


thats it, hope it helps

The difference between staticmethod and classmethod in python

well, since i am a person that depend heavily on the vast opensource community as a hough resource of knowledge. I like to be able to contribute with the little knowledge that i gain.
So today i will explain the difference between staticmethod and classmethod in python, lets start..

You may have read a couple of python books/tutorials and i think that none of them mentions the difference between the staticemethod and classmethod decorator, even some tutorials says that there is no difference at all !!!

Why would i need to use static/class methods?

static/class methods are methods that binded to the class they created in not the object of that class, so you dont need to make an instance object of the class to call these methods, and it is used when your method doesnot depend on any object specific attributes.

Example of static method:

class FactoryClass(object):
@staticmethod
def createObject(objectType):
do some stuff

the code just define a class called FactoryClass and define a static method in this class called createOject, so how would it be to do the same using class method

Example of class method:

class FactoryClasss(object):

@classmethod

def createObject(cls, objectType):

do some stuff

so not so much of a difference ha, the only thing that is different is that the class method is passed the class object by default as its first paramter, so what i can do wiht the class object paramters ?

lets say that you not only want to create object of a certain type but also you want to make sure that at any point of time there is only one instance object of each type.

Ok easy, the first thing you would think of is to create an attribute(map) that hold each type as key and the value is the object and in the createObject method you will check if the type already exits in the map, then you will not create any new instance but will return the already created one, lets do that

Using class method:

class ClassFactory(object):

objectMap = dict()

classMap = {'type1': Class1, 'type2': Class2}

@classmethod

def createObject(cls, objectType):

if objectType in cls.objectMap:

return cls.objectMap.get(objectType)

else:

object = cls.classMap.get(objectType)

cls.objectType[objectType] = object

return object

pretty neat ha, but it does not mean you cannot do that using a static method, the thing is that it will not be as clean as the class method one, lets have a look

Using static method:

class ClassFactory(object):

objectMap = dict()

classMap = {'type1': Class1, 'type2': Class2}

@staticmethod

def createObject(objectType):

if objectType in ClassFactory.objectMap:

return ClassFactory.objectMap.get(objectType)

else:

object = ClassFactory.classMap.get(objectType)

ClassFactory.objectType[objectType] = object

return object

hope it helps...

[CES 2010] RCA Airnergy Charger Harvests Electricity From WiFi Signals

well this is very cool stuff...

the idea here is that the device is kind of circuitry that harvests the WiFi energy out of the air and convert it to electricity.
The device(Airnergy) has a small battery in it, so you can just carry it around and as long as there is a WiFi near you, it charges itself.
The great news is the device will be out in the market soon for 40$ !!!

for more info check that blog

Google wants to administer the first white spaces database

http://www.infoq.com/news/2010/01/Google-White-Spaces-Database

pretty cool..

How to decode a URL using python

I was doing a task and i needed a function to decoded a url as a dictionary of parameters and its values,

since i used urllib.urlencode before i was sure that i will find urllib.decode method as well, but i didn't.

Here is the result of my search, to decode a url into dictionary of parameter and its values user the cgi module as the follwoing:

import cgi

import urllib

url = 'http://www.test.com/test?%s'

params = {'param1': 'value1', 'param2': 'value2'}

urlParams = urllib.urlencode(params)

url = url%urlParams

resultParams = dict(cgi.parse_qsl(url))

print result_params

Enjoy

Notes on REST Architecture

REST stands for Representation State Transfer

the main characteristics of REST are:

• Distributed Network of interlinked documents
• Client-server architecture
• Stateless Server
• The concept of Resource and Resource Representation

the action of retrieving a resource must be Idempotent, the fact that you made the request should not change the contents of the resource.

From "Beginning Python 2005"

My trip to my hometown

I am traveling to my home city and while i am at the train i see the life of the way to the upper egypt and i wonder how ignorant i was, how much i dont know about my own country and the people who i share with them a religion , home and a future.

the thing that striks me is how different the life here from the crowded city of cairo, how peacefull the people are and how beautiful our upper egypt is.

Today i visited my grandparents grave and i got a feeling my words cannot help me explaining them, but one of the feelings is definitaly sadness, i was sad because the memories that suddenlly became like reality, i got the feeling that my grandfather have past away only yesterday and there is nothing compared to that feeling, those kind of feelings that makes even taking your bearth very defficult process.

and there were the part where i just sat there at this beautifull place outside the mosque, where the wheher cannot be better(the weather was one of the things that made me hisitate going on this trip).

Google engineers takes python to the next level

Great news for all python fans, Google engineers are working on a project to create a Just In Time (JIT) compiler for python programming language to be used instead of the python virtual machine.
The project called Unladen Swallow and promises a five time faster python.
you can read more details about this great news here

Linux Tips

How to take the output of a command and pass it as arguments to another command ?

• using pips
  
• using xargs: $ ls /bin/b& | xargs -t dpkg-query -S

How to watch commads:

• $ watch -n 10 'ls -la'
• $ watch -d 'ls -la'

Using bash history:

• $ history
• $ ! 33
• $ ! !
• $ ! ls:s/CF/1

Bash: the shell
there are two types of files holding the bash settings, startup files and initialization files

• startup files: runs for any shell that is a login shell (/etc/profile/.bash_profile, .profile, and .bash_login)
• initialization files: runs for interactively running shells (not shell scripts) (/etc/bash.bashrc, ~/.bashrc)

sudo:

• every use of sudo gets logged in /var/log/secure
  

Back with some Networking

What is Network secure communication components?

• Confidentiality: only the sender and the intended receiver should be able to understand the content of the transmitted massege
• Authentication: both the sender and receiver should be able to confirm the identity of the other party  involved in the communication
• Message integrity and unrepudation: making sure that the content of the communication estalished between to authenticated entities has not be altered
• Availability and access control: making sure that legitimate user can access the network services(Denail of service attacks prevention)

Today's mix: Geography, algorithms,....

Recurrence Equation

What is a Recurrence Equation?
it is a mathematical equation where the value of the function at a given n is given in terms of the value of the function in a smaller value of n

recurrence equation is used in algorthmis analysis to represent recursive functions,like a recursive function, a recurrence equation needs an intial condtion where the call stack will stop evenually at.

Example Fabonanci function:


input: non-negative number n
output: n!
Algorthim:
int fact (int n) {
if (n == 0) return 1;
else return n * fact (n - 1);
}
suppose that t(n) is the number of multiplication done for a given value of n:
t(n) = t(n-1) + 1 where n >= 1
t(0) = 0
The above equation is a Recurrence equation it conforms the tow conditions stated in the definition mentioned earlier:

1. it have an initial condition --> t(0) = 0
   
2. the value of the equation at n is in-terms of the value of the same equation with a smaller n (n-1 in out example)
   

Stuff l learned today

Tail Recursion optimization:

it is the process of converting a recursive function call to an iterative procedure providing that the recursive call is the last call in the function with no other operations after it.

Napoleon and Divide-and-Conquer

Today i learned how the French emperor Napoleon is related to the computer programming algorithm technique Divide-and-Conquer.

It was December 2, 1805 on the battle of Austerlitz when Napoleon was faced with an Astro-Russein army which out-numbered his with 15,000 solider, so Napoleon drove right into the middle of the enemy's army to splite it into a tow smaller armies which each of them is weaker than his army.
The Astro-Russein two splitted armies each suffered heavy losses and were compelled to retreat.

From the previous story the technique of Divide-and-Conquer were developed that for some instance of a problem, if the instance can be divided into smaller instance of the same problem, then the solution for the original instance can be obtained from the solution of the smaller one's

Today it is AJax

What is Comet(reverse Ajax)?

it is the illusion that data being pushed from the server.
for example:

a web aggregator that fetch feeds from different sources and view it to the user, the data may viewed as it is being pushed from the server using Comet

How it works ?

a separate process is responsible for fetching data from the server perodically, then it pushes these data to the aggregator

Today's new stuff

Today I am going to learn something totally new.It is about the ocean and why the ocean colour is blue.


Why the ocean colour is blue?

it is the transmission of energy that makes the ocean colour blue, how?
when the sunlight which contains colours hits the oceans surface, the water molecules scatter the light rays.This scattering causes the water to appear blue because the blue light of the sun rays scatters more than any light of other colours.
source "HowStuffworks.com"

Today's stuff

Nybble:

           nybble is a term in computing called for a half of byte (4 bits)

Stuff l learned today

Glib-GObject Signal:
Signals - A means for customization of object behavior and a general purpose notification mechanism "GObject Signal API"

The older man alive:
Tomoji Tanabe is the older alive man, he is celebrating his 113th birthday today :)