import os
import wiringpi
from time import sleep

os.system( 'gpio export 4 out' )
sleep (0.5)

io = wiringpi.GPIO(wiringpi.GPIO.WPI_MODE_SYS)
io.pinMode(4,io.OUTPUT)

while True:
    io.digitalWrite(4,1)
    sleep(1)
    io.digitalWrite(4,0)
    sleep(1)