ardu_pi_i2c.py

import smbus
import time

# for RPI version 1, use "bus = smbus.SMBus(0)"
bus = smbus.SMBus(1)

# This must match in the Arduino Sketch
SLAVE_ADDRESS = 0x04

def request_reading():
    reading = int(bus.read_byte(SLAVE_ADDRESS))
    print(reading)


while True:
    command = raw_input("Enter command: l - toggle LED, r - read A0 ")
    if command == 'l' :
        bus.write_byte(SLAVE_ADDRESS, ord('l'))
    elif command == 'r' :
        request_reading()