在子进程 python 中通过 child 调用 parent 实例

Question

我有一个文件 parent.py，它使用子进程调用它的 child child.py。类似这样：

p = subprocess.Popen(["C:/Users/.../child.py", some_arg1, some_arg2],shell=True, stdout=subprocess.PIPE, stderr=subprocess.PIPE, stdin=subprocess.PIPE)

在 child 进程启动后，我想将一个变量从 child 进程发送到 parent 进程。 child 不应在完成时发送消息，而是在执行的某个时刻发送消息。我怎样才能做到这一点？搜索了几个小时后，我似乎只能找到相反的解决方案（从 Parent 到 child）。感谢您的帮助。

Answer 1

有几种方法可以促进这种 inter-process 交流。一种更常见的方法是使用 first-in-first-out (FIFO) 命名管道。

这是一个非常基本的演示。

parent.py:

#! /usr/bin/env python3

import os, tempfile, subprocess

# make a temp directory that's automatically removed when we're done
with tempfile.TemporaryDirectory() as dir:

    # create a FIFO in that directory
    fifo_path = os.path.join(dir, 'fifo')
    os.mkfifo(fifo_path)

    # start the child process
    proc = subprocess.Popen(['./child.py', '--fifo', fifo_path])
    print('process started')

    # open the FIFO
    with open(fifo_path, 'r') as fifo:

        # read output from the child process
        mid_output = fifo.readline()
        print(f'{mid_output = }')

        # wait for child to finish
        code = proc.wait()
        print(f'process finished')

child.py:

#! /usr/bin/env python3

import argparse, time

# read FIFO path from command line
parser = argparse.ArgumentParser()
parser.add_argument('--fifo', required=True)
args = parser.parse_args()

# open FIFO (created by parent)
with open(args.fifo, 'w') as fifo:

    # simulate some work being done
    time.sleep(1)

    # tell the parent that progress has been made
    fifo.write('Halfway there!\n')
    fifo.flush()  # make sure to flush FIFOs

    # Simulate some more work being done
    time.sleep(1)

然后，它运行如下：

./parent.py
process started
mid_output = 'Halfway there!\n'
process finished

您可以让 child 脚本输出它需要对 parent 说的任何内容，并且您可以让它这样做多次。只需确保 parent 知道从 child 读取的次数与 child 写入的次数相同。

在子进程 python 中通过 child 调用 parent 实例

Calling parent instance thru child in subprocess python

python

python-3.x

subprocess

popen