如何在运行过程中获取子进程输出？

Question

我有两个文件 main.py 和 infinit.py，如下所示：

main.py

#!/usr/bin/python

import logging
import subprocess
import sys

logging.basicConfig(level=logging.INFO)


def forever():
    cmd = [sys.executable, 'infinit.py']
    while 1:
        try:
            print 'running new instance of:'
            print ' '.join(cmd)
            popen = subprocess.Popen(cmd, stdout=subprocess.PIPE,
                stderr=subprocess.PIPE, universal_newlines=True)

            for line in iter(popen.stderr.readline, ""):
                print line,
            for line in iter(popen.stdout.readline, ""):
                print line,

        except Exception as e:
            print 'Something bad happend'
            logging.error(e)


if __name__ == '__main__':
    forever()

infinit.py

#!/usr/bin/python

import logging

logging.basicConfig(level=logging.INFO)

i = 0
while 1:
    i += 1
    logging.info('i: {0}'.format(i))
    print i

我运行 main.py 并希望在我的控制台中同时查看（打印和日志记录）。 我也希望它在 windows 和 linux 上运行。 此外，它是否可以在 Windows Idle 中工作（打印和记录）？

Answer 1

在你的程序的乞求处添加这一行，并放入相同的LOG_FILENAME，然后你可以使用tail -f unix命令查看输出。

import logging
logging.basicConfig(filename=LOG_FILENAME,level=logging.DEBUG, filemode = 'w+')
logging.getLogger().setLevel(logging.DEBUG)

Answer 2

我找到了两种解决方案，它们都应该适用于 Linux 和 Windows，甚至适用于 Windows Idle：

1. 更简单：

在父进程中打印子进程的stderr：

#!/usr/bin/python

import logging
import subprocess
import sys

def forever():
    cmd = [sys.executable, 'infinit.py']
    while 1:
        try:
            print 'running new instance of:'
            print ' '.join(cmd)
            popen = subprocess.Popen(cmd, stdout=subprocess.PIPE,
                stderr=subprocess.PIPE, universal_newlines=True)

            for line in iter(popen.stderr.readline, ""):
                print line,

        except Exception as e:
            print 'Something bad happend'
            logging.error(e)

if __name__ == '__main__':
    forever()

现在：

• 父打印子日志（因为默认情况下日志将消息发送到我们正在打印的标准错误和标准错误）
• 父不打印子打印，所以：

infinit.py

#!/usr/bin/python

import logging
import sys
import time

logging.basicConfig(level=logging.INFO)

sys.stdout = sys.stderr

i = 0
while 1:
    i += 1
    logging.info('i: {0}'.format(i))
    print i
    time.sleep(0.2)

1. 这里有另一种方法：

Intercepting stdout of a subprocess while it is running

我的代码适应了解决方案

main.py

#!/usr/bin/python

import logging
import subprocess
import sys

def forever():
    CMD = [sys.executable, 'infinit.py']
    while 1:
        try:
            print 'running new instance of:'
            print ' '.join(CMD)

            popen = subprocess.Popen(CMD, stdout=subprocess.PIPE)
            for line in iter(popen.stdout.readline, ""):
                print line,

        except Exception as e:
            print 'Something bad happend'
            logging.error(e)
        finally:
            print


if __name__ == '__main__':
    forever()

init.py

#!/usr/bin/python

import logging
import sys
import time


class FlushFile(object):
    """Write-only flushing wrapper for file-type objects."""
    def __init__(self, f):
        self.f = f
    def write(self, x):
        self.f.write(x)
        self.f.flush()

logging.basicConfig(level=logging.INFO)

sys.stdout = FlushFile(sys.stdout)


i = 0
while 1:
    i += 1
    logging.info('i: {0}'.format(i))
    print i
    time.sleep(0.2)