python subprocess模块 监控子进程的2种方式 忙等待和立即返回同时设置子进程超时时间

import subprocess
import os
import time
tt = '555'
cmd = "python /home/pidancode/python/mypython/sub2.py "+" 333"+" 444 "+tt
print(time.time())
sub2 = subprocess.Popen(cmd, shell=True)
while 1:
    ret1 = subprocess.Popen.poll(sub2)
    if ret1 == 0:
        print(sub2.pid,'end')
        break
    elif ret1 is None:
        print()'running')
        time.sleep(1)
    else:
        print(sub2.pid,'term')
        break 
print(time.time())

import subprocess  
import select  
import time  
import signal  
import os  
tt = '555'  
cmd = "python /home/pidancode/python/mypython/sub2.py "+" 333"+" 444 "+tt
timeout = 3
pro = subprocess.Popen(cmd, stdout=subprocess.PIPE,shell = True)
print(time.time())
while 1:
    while_begin = time.time()
    print('timeout',timeout)
    fs = select.select([pro.stdout], [], [], timeout)
    if pro.stdout in fs[0]:
        tmp = pro.stdout.read()
        print('read', tmp)
        if not tmp:
            print('end')
            print(time.time())
            break
    else: 
        print('outoftime')
        print(os.kill(pro.pid, signal.SIGKILL))
        break 
    timeout = timeout - (time.time() - while_begin)