With this project we're interfacing Python and Arduino over serial.

The first try was to control a LED from the keyboard.

First, the Arduino part, that read on serial :

/*
  Blink
  Turns on an LED on for one second, then off for one second, repeatedly.

  This example code is in the public domain.
 */

// Pin 13 has an LED connected on most Arduino boards.
// give it a name:
int led = 13;

// the setup routine runs once when you press reset:
void setup() {
  // initialize the digital pin as an output.
  Serial.begin(57600);
  pinMode(led, OUTPUT);
}

// the loop routine runs over and over again forever:
void loop() {
  if(Serial.available() >= 1){
    if (byte(Serial.read())==0) {
      digitalWrite(led, LOW);    // turn the LED off by making the voltage LOW
    }
    else {
      digitalWrite(led, HIGH);   // turn the LED on (HIGH is the voltage level)
    }
  }
}

Then, the Python part, that read from keyboard and write to serial :

# -*- coding: utf-8 -*-
import serial

# Setup the Serial Object
ser = serial.Serial()
# Set the Serial Port to use
ser.setPort("/dev/ttyACM0")
# Set the Baudrate (Arduino Sketch is expecting 57600 for smooth transitions in the GUI)
ser.baudrate = 57600
# Open the Serial Connection
ser.open()
loopVar = True

import time

i = 0
if (ser.isOpen()):
  # Start a main loop
  while (loopVar):
    i += 1
    car = raw_input("Entrer un car ")
    if car == 'a' :
      print 'allume'
      ser.write('a')
    elif car == 'q' :
      break
    else :
      print 'éteint'
      ser.write('\0')
  ser.close()