Simple Port Chaser for PCF8574 on I2C on Raspberry Pi REV1

#!/usr/bin/python
from smbus import SMBus
from itertools import cycle
from time import sleep

IOEXTADDR = 0x38 # I2C adresse des PCF8574 IO Extenders

PAT0 = 0xff              # Alle Pins HIGH schaltet alle relais aus.
PAT1 = int('11111110',2) # Relais 1 ein
PAT2 = int('11111101',2) # Relais 2 ein
PAT3 = int('11111011',2) # Relais 3 ein
PAT4 = int('11110111',2) # Relais 4 ein

PATTERN = (PAT1,PAT2,PAT3,PAT4)

bus = SMBus(0) # I2C Port 0 auf REV 1 boards(!)

for DATABYTE in cycle(PATTERN):
    bus.write_byte(IOEXTADDR, DATABYTE)
    sleep(0.5)
    bus.write_byte(IOEXTADDR, PAT0)
    sleep(0.5)