在运行过程中如何获取子进程输出？

Question

我有2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()

无穷大

#!/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，我想在控制台中同时看到（打印和日志记录）。 我也希望它在Windows和Linux上运行。 另外，它是否可以在Windows空闲状态下工作（打印和记录）？

Answer 1

在程序开始时添加此行，并输入相同的LOG_FILENAME，然后可以使用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

我发现了两个解决方案，它们都可以在Linux和Windows甚至Windows Idle上运行：

1. 简单的：

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()

目前：

• 父级打印子级日志记录（因为默认情况下，日志记录会向我们正在打印的stderr adn stderr发送消息）
• 家长不打印儿童印刷品，因此：

无穷大

#!/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)

2. 另一个方法是在这里：

在子进程运行时拦截它的stdout

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()

inifinit.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)