python定时检查某个进程是否已经关闭的方法

import threading
import time
import os
import subprocess
def get_process_count(imagename):
p = os.popen('tasklist /FI "IMAGENAME eq %s"' % imagename)
return p.read().count(imagename)
def timer_start():
t = threading.Timer(120,watch_func,("is running..."))
t.start()
def watch_func(msg):
print "I'm watch_func,",msg
if get_process_count('main.exe') == 0 :
print subprocess.Popen([r'D:shuajibinmain.exe'])
timer_start()
if __name__ == "__main__":
timer_start()
while True:
time.sleep(1)