Question

我正在使用subprocess.Popen（）执行命令。我想在执行剩下的代码之前等待进程完成但同时我想在运行子进程2分钟后检查生成的文件的状态。如果文件的大小为零，那么我想停止该过程。目前我的代码如下。有没有更聪明的方法呢？

  def execute(command,outputfilename):
    process = subprocess.Popen(command, stdout=subprocess.PIPE, stderr=subprocess.STDOUT)
    start_time=time.time()
    Is_Working=False
    while True:
     process.poll()
     if not Is_Working:
         #allow 2 minutes for the process to create results
         if process.returncode == None and (time.time()-start_time)//60>1:
             Is_Working=True
             if (os.stat(outputfilename)[6]==0):
                 process.kill()
                 return
     if process.returncode != None: 
         break

    output, errors=process.communicate()

Answer 1

全球你的代码对我来说很好。只有几个细节：

在(time.time()-start_time)//60>1中，我认为使用//是无用的，因为你不一定需要对结果进行平局，并将整数转换为除法的lhs的结果。保持全部浮动应该可以进行比较，这是所有基本的机器逻辑;
通过使用while process.returncode is not None:…
为了使它更简单，我实际上会循环直到文件大小为!=0，然后在循环之后调用process.wait()。
这将是使用while/else构造

所以，一个改进是，所以你可以在过程完成后做任务（比如清理或重试......）（无论是成功还是失败）：

def execute(command,outputfilename):
    process = subprocess.Popen(command, stdout=subprocess.PIPE, stderr=subprocess.STDOUT)
    start_time=time.time()
    Is_Working=False
    while process.returncode == None:
        process.poll()
        #allow 2 minutes for the process to create results
        if (time.time()-start_time)/60 > 1:
            if (os.stat(outputfilename)[6]==0):
                process.kill()
                break
    else:
        # the process has not been killed
        # wait until it finishes
        process.wait()
        output, errors=process.communicate()
        # do stuff with the output
        […]

    # here the process may have been killed or not
    […]

或另一个好的选择是提出例外：

def execute(command,outputfilename):
    process = subprocess.Popen(command, stdout=subprocess.PIPE, stderr=subprocess.STDOUT)
    start_time=time.time()
    Is_Working=False
    while process.returncode == None:
        process.poll()
        #allow 2 minutes for the process to create results
        if (time.time()-start_time)/60 > 1:
            if (os.stat(outputfilename)[6]==0):
                process.kill()
                raise Exception("Process has failed to do its job")
    # the process has not been killed
    # wait until it finishes
    process.wait()
    output, errors=process.communicate()
    # do stuff with the output
    […]

HTH

Answer 2

如果outputfilename为空（我假设某些外部流程修改了outputfilename），要在2分钟内终止子流程，您可以使用threading.Timer：

import os
from subprocess import Popen, PIPE
from threading import Timer

def kill_if_empty(proc, filename):
    if proc.poll() is None and os.path.getsize(filename) == 0:
       proc.kill()

def execute(command, outputfilename):
    p = Popen(command, stdout=PIPE, stderr=PIPE)
    Timer(2*60, kill_if_empty, [p, outputfilename]).start()
    output, errors = p.communicate()
    ...

此代码分别收集stdout / stderr，它避免了问题中代码中可能存在的死锁。

运行子进程时检查条件

2 个答案: