ping periodically and print results

log_ping

import subprocess
import sched
import threading
from functools import partial
import time
from datetime import datetime

def ping( host, count=1, timeout=5):
    count, timeout= map(str, (count, timeout))
    devnull= open("/dev/null","w")
    result= subprocess.call( ["ping", "-c", count, "-w", timeout, host], stdout=devnull, stderr=devnull)
    return result==0

def repeat( f,  interval ):
    extra= 0.5-(datetime.utcnow().microsecond/1000000.0) #try to fire event always on the middle of system second
    extra*=0.01 #gradual
    stable_interval= interval+extra #avoid accumulated error because of function call time
    if keep_running:
        threading.Timer(stable_interval, repeat, (f,interval) ).start()
        f()

def log(f):
    date, result= datetime.utcnow(), f()
    log_lock.acquire()
    print date,result
    log_lock.release()

log_lock= threading.Lock()
keep_running=True
ping_f= partial(ping, "yahoo.com", timeout=1)
log_f= partial(log, ping_f)
repeat( log_f, 1)
while True:
    try:
        time.sleep(1)
    except KeyboardInterrupt:
        keep_running=False
        break