用于记录的上下文管理器等效于 contextmanager=>yield stdout答案

【问题标题】：Context manager for logging equivalent to contextmanager=>yield stdout用于记录的上下文管理器等效于 contextmanager=>yield stdout
【发布时间】：2017-05-04 02:59:07
【问题描述】：

我正在使用的库采用如下函数：

@contextlib.contextmanager
def stdout_cm():
    yield sys.stdout

现在我如何通过logging 实例而不是foo(stdout_cm) 将tees 发送到多个处理程序？（标准输出和 StringIO）

尝试：

from sys import stdout, stderr
from cStringIO import StringIO
from logging import getLogger, basicConfig, StreamHandler
from subprocess import check_call

basicConfig(format='%(asctime)s %(name)-12s %(levelname)-8s %(message)s',
            datefmt='%m-%d %H:%M', level='INFO')

log = getLogger(__name__)
console = StreamHandler(StringIO())

log.addHandler(console)
log.addHandler(StreamHandler(stdout))

class LoggerContext(object):
    def __init__(self, logger, level=None, close=True):
        self.logger = logger
        self.level = level
        self.close = close

    def __call__(self):
        return self

    def __enter__(self):
        if self.level is not None:
            self.old_level = self.logger.level
            self.logger.setLevel(self.level)

    def __exit__(self, et, ev, tb):
        if not self.close:
            return
        for handler in self.logger.handlers:
            handler.close()

简化函数：

def foo(f):
    with f() as fh:
        check_call(["printf '\n\n' | wc -l"], shell=True, stderr=fh, stdout=fh)

foo(LoggerContext(log)) #, level='WARN')


print console.stream.getvalue()

【问题讨论】：

嗯 - stackoverflow.com/a/4838875

标签： python logging subprocess contextmanager stringio

【解决方案1】：

前奏：

import os
import logging
import subprocess

from io import IOBase
from sys import stdout
from select import select
from threading import Thread
from time import sleep

log = logging.getLogger(__name__)

类（基于https://stackoverflow.com/a/4838875）：

class StreamLogger(IOBase):
    _run = None

    def __init__(self, logger_obj, level):
        super(StreamLogger, self).__init__()
        self.logger_obj = logger_obj
        self.level = level
        self.pipe = os.pipe()
        self.thread = Thread(target=self._flusher)
        self.thread.start()

    def __call__(self): return self

    def _flusher(self):
        self._run = True
        buf = b''
        while self._run:
            for fh in select([self.pipe[0]], [], [], 1)[0]:
                buf += os.read(fh, 1024)
                while b'\n' in buf:
                    data, buf = buf.split(b'\n', 1)
                    self.write(data.decode())
            sleep(1)
        self._run = None

    def write(self, data): return self.logger_obj.log(self.level, data)
    def fileno(self): return self.pipe[1]

    def close(self):
        if self._run:
            self._run = False
            while self._run is not None:
                sleep(1)
            os.close(self.pipe[0])
            os.close(self.pipe[1])

用法：

with StreamLogger(log, logging.INFO) as out, StreamLogger(log,
                                                          logging.ERROR) as err:
    subprocess.Popen('ls 1>&2', stderr=err, shell=True)

【讨论】：