即使直接子进程已终止，Popen 也会等待子进程

Popen waiting for child process even when the immediate child has terminated(即使直接子进程已终止，Popen 也会等待子进程)

问题描述

我在 Windows 8/XP 上使用 Python 2.7.

I'm working with Python 2.7 on Windows 8/XP.

我有一个程序 A 使用以下代码运行另一个程序 B:

I have a program A that runs another program B using the following code:

p = Popen(["B"], stdout=PIPE, stderr=PIPE)
stdout, stderr = p.communicate()
return

B 运行批处理脚本 C.C 是一个长时间运行的脚本，即使 C 尚未完成，我也希望 B 退出.我已经使用以下代码(在 B 中)完成了它:

B runs a batch script C. C is a long running script and I want B to exit even though C has not finished. I have done it using the following code (in B):

p = Popen(["C"])
return

当我运行 B 时，它按预期工作.但是，当我运行 A 时，我希望它在 B 退出时退出.但是即使 B 已经退出，A 也会等到 C 退出.关于正在发生的事情以及可能的解决方案有什么想法吗?

When I run B, it works as expected. When I run A however, I expected it to exit when B exits. But A waits until C exits even though B has already exitted. Any ideas on what's happening and what possible solutions could be?

不幸的是，将 A 更改为 B 的明显解决方案是不可行的.

Unfortunately, the obvious solution of changing A to look like B is not an option.

以下是说明此问题的功能示例代码:https://www.dropbox.com/s/cbplwjpmydogvu2/popen.zip?dl=1

Here is a functional sample code to illustrate this issue: https://www.dropbox.com/s/cbplwjpmydogvu2/popen.zip?dl=1

非常感谢任何意见.

推荐答案

您可以为 C 子进程提供 start_new_session 模拟:

You could provide start_new_session analog for the C subprocess:

#!/usr/bin/env python
import os
import sys
import platform
from subprocess import Popen, PIPE

# set system/version dependent "start_new_session" analogs
kwargs = {}
if platform.system() == 'Windows':
    # from msdn [1]
    CREATE_NEW_PROCESS_GROUP = 0x00000200  # note: could get it from subprocess
    DETACHED_PROCESS = 0x00000008          # 0x8 | 0x200 == 0x208
    kwargs.update(creationflags=DETACHED_PROCESS | CREATE_NEW_PROCESS_GROUP)  
elif sys.version_info < (3, 2):  # assume posix
    kwargs.update(preexec_fn=os.setsid)
else:  # Python 3.2+ and Unix
    kwargs.update(start_new_session=True)

p = Popen(["C"], stdin=PIPE, stdout=PIPE, stderr=PIPE, **kwargs)
assert not p.poll()

[1]: CreateProcess 的进程创建标志()

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