在 n 秒后终止 python 中的函数调用

Question

我的 python 代码是这样的：

def a():
    ...  
    ...  
    subprocess.call()  
    ...  
    ...  

def b():  
    ...  
    ...

等等。

我的任务：
1) 如果 subprocess.call() returns 在 3 秒内，我的执行应该在 subprocess.call() returns.
的那一刻继续 2) 如果 subprocess.call() 在 3 秒内没有 return，则 subprocess.call() 应该终止，我的执行应该在 3 秒后继续。
3) 直到 subprocess.call() returns 或 3 秒结束，不应再执行。

这可以用线程来完成，但是怎么做呢？

真实代码的相关部分是这样的：

...  
cmd = ["gcc", "-O2", srcname, "-o", execname];    
p = subprocess.Popen(cmd,stderr=errfile)//compiling C program  
...  
...  
inputfile=open(input,'w')  
inputfile.write(scanf_elements)  
inputfile.close()  
inputfile=open(input,'r')  
tempfile=open(temp,'w')
subprocess.call(["./"+execname,str(commandline_argument)],stdin=inputfile,stdout=tempfile); //executing C program
tempfile.close()
inputfile.close()  
...  
...

我正在尝试使用 python 编译和执行 C 程序。当我使用 subprocess.call() 执行 C 程序时，假设 C 程序包含无限循环，那么 subprocess.call() 应该在 3 秒后终止，程序应该继续。我应该能够知道 subprocess.call() 是被强制终止还是成功执行，以便我可以相应地在以下代码中打印消息。

后端gcc属于linux.

Answer 1

如果您愿意将调用转换为 Popen 构造函数而不是 call（与运行 gcc 相同），那么一种方法是方法是等待 3 秒，轮询子进程，然后根据它的 returncode 属性是否仍然是 None 来采取行动。考虑以下高度人为的示例：

import sys
import time
import logging
import subprocess

logging.basicConfig(format='%(asctime)s %(levelname)s %(message)s', level=logging.INFO)

if __name__ == '__main__':
  logging.info('Main context started')
  procCmd = 'sleep %d' % int(sys.argv[1])
  proc = subprocess.Popen(procCmd.split())

  time.sleep(3)
  if proc.poll() is None:
    logging.warning('Child process has not ended yet, terminating now')
    proc.terminate()
  else:
    logging.info('Child process ended normally: return code = %s' % str(proc.returncode))

  logging.info('Main context doing other things now')
  time.sleep(5)
  logging.info('Main context ended')

这会导致不同的日志输出，具体取决于子进程是否在 3 秒内完成：

$ python parent.py 1
2015-01-18 07:00:56,639 INFO Main context started
2015-01-18 07:00:59,645 INFO Child process ended normally: return code = 0
2015-01-18 07:00:59,645 INFO Main context doing other things now
2015-01-18 07:01:04,651 INFO Main context ended
$ python parent.py 10
2015-01-18 07:01:05,951 INFO Main context started
2015-01-18 07:01:08,957 WARNING Child process has not ended yet, terminating now
2015-01-18 07:01:08,957 INFO Main context doing other things now
2015-01-18 07:01:13,962 INFO Main context ended

请注意，即使子进程比这更早完成，上述方法也会始终等待 3 秒。如果您想要不同的行为，您可以将上面的代码转换成一个循环，不断轮询子进程——您只需要跟踪已经过去了多少时间。

Answer 2

#!/usr/bin/python

import thread
import threading
import time
import subprocess
import os 

ret=-1

def b(arg):
    global ret
    ret=subprocess.call(arg,shell=True);

thread.start_new_thread(b,("echo abcd",))
start = time.time()


while (not (ret == 0)) and ((time.time() - start)<=3):
    pass

if (not (ret == 0)) :
    print "failed"
    elapsed = (time.time() - start)
    print elapsed
    thread.exit()

elif (ret == 0):#ran before 3 sec
    print "successful"
    elapsed = (time.time() - start)
    print elapsed

我已经编写了上面的代码，它可以正常工作并满足我的所有限制。 link https://docs.python.org/2/library/thread.html 表示：

thread.exit() 引发 SystemExit 异常。当没有被捕获时，这将导致线程静默退出。

所以我想应该不会出现孤儿进程、资源阻塞等问题，请指教

Answer 3

My task:
1) If subprocess.call() returns within 3 seconds, my execution should continue the moment subprocess.call() returns.
2) If subprocess.call() does not return within 3 seconds, the subprocess.call() should be terminated and my execution should continue after 3 seconds.
3) Until subprocess.call() returns or 3 seconds finishes, the further execution should not take place.

在 *nix 上，您可以使用 signal.alarm()-based solution:

import signal
import subprocess

class Alarm(Exception):
    pass

def alarm_handler(signum, frame):
    raise Alarm

# start process
process = subprocess.Popen(*your_subprocess_call_args)

# set signal handler
signal.signal(signal.SIGALRM, alarm_handler)
signal.alarm(3) # produce SIGALRM in 3 seconds

try:
    process.wait() # wait for the process to finish
    signal.alarm(0) # cancel alarm
except Alarm: # subprocess does not return within 3 seconds
    process.terminate() # terminate subprocess
    process.wait()

这是一个基于 threading.Timer() 的便携式解决方案：

import subprocess
import threading

# start process
process = subprocess.Popen(*your_subprocess_call_args)

# terminate process in 3 seconds
def terminate():
    if process.poll() is None:
        try:
            process.terminate()
        except EnvironmentError:
            pass # ignore 

timer = threading.Timer(3, terminate)
timer.start()
process.wait()
timer.cancel()

Answer 4

下面的代码终于起作用了：

import subprocess
import threading
import time


def process_tree_kill(process_pid):
    subprocess.call(['taskkill', '/F', '/T', '/PID', process_pid])

def main():
    cmd = ["gcc", "-O2", "a.c", "-o", "a"];  
    p = subprocess.Popen(cmd)
    p.wait()
    print "Compiled"
    start = time.time()

    process = subprocess.Popen("a",shell=True)
    print(str(process.pid))   

    # terminate process in timeout seconds
    timeout = 3 # seconds
    timer = threading.Timer(timeout, process_tree_kill,[str(process.pid)])
    timer.start()

    process.wait()
    timer.cancel()

    elapsed = (time.time() - start)
    print elapsed

if __name__=="__main__":
    main()

在 n 秒后终止 python 中的函数调用

terminating a function call in python after n seconds

c

linux

subprocess

python-2.7