将Python'print'输出重定向到Logger

Question

我有一个Python脚本,它使用'Print'打印到stdout.我最近通过Python Logger添加了日志记录,并希望如果启用了日志记录,这些打印语句将转到logger.我不想修改或删除这些打印语句.

我可以通过'log.info("some info msg")'来记录.我希望能够做到这样的事情:

if logging_enabled:
  sys.stdout=log.info
print("test")

如果启用了日志记录,则应记录"test",就像我执行log.info("test")一样.如果未启用日志记录,则只应将"test"打印到屏幕上.

这可能吗？我知道我可以以类似的方式将stdout指向文件(请参阅:重定向打印到日志文件)

Answer 1

您有两种选择:

1. 打开一个日志文件并用它替换sys.stdout,而不是函数:

   log = open("myprog.log", "a")
   sys.stdout = log
   
   >>> print("Hello")
   >>> # nothing is printed because it goes to the log file instead.
   

2. 用您的日志功能替换打印:

   # If you're using python 2.x, uncomment the next line
   #from __future__ import print_function
   print = log.info
   
   >>> print("Hello!")
   >>> # nothing is printed because log.info is called instead of print
   

Answer 2

当然,您可以打印到标准输出并附加到日志文件,如下所示:

# Uncomment the line below for python 2.x
#from __future__ import print_function

import logging

logging.basicConfig(level=logging.INFO, format='%(message)s')
logger = logging.getLogger()
logger.addHandler(logging.FileHandler('test.log', 'a'))
print = logger.info

print('yo!')

Answer 3

还有一种方法是将记录器包装在一个对象中,该对象将调用转换write为记录器的log方法.

Ferry Boender就是这样做的,根据GPL许可证在他的网站上的帖子中提供:

import logging
import sys

class StreamToLogger(object):
   """
   Fake file-like stream object that redirects writes to a logger instance.
   """
   def __init__(self, logger, log_level=logging.INFO):
      self.logger = logger
      self.log_level = log_level
      self.linebuf = ''

   def write(self, buf):
      for line in buf.rstrip().splitlines():
         self.logger.log(self.log_level, line.rstrip())

logging.basicConfig(
   level=logging.DEBUG,
   format='%(asctime)s:%(levelname)s:%(name)s:%(message)s',
   filename="out.log",
   filemode='a'
)

stdout_logger = logging.getLogger('STDOUT')
sl = StreamToLogger(stdout_logger, logging.INFO)
sys.stdout = sl

stderr_logger = logging.getLogger('STDERR')
sl = StreamToLogger(stderr_logger, logging.ERROR)
sys.stderr = sl

这使您可以轻松地将所有输出路由到您选择的记录器.如果需要,您可以在替换之前保存sys.stdout和/或sys.stderr按照其他人的提及,如果您需要稍后恢复它.

Answer 4

一个更简单的选择

import logging, sys
logging.basicConfig(filename='path/to/logfile', level=logging.DEBUG)
logger = logging.getLogger()
sys.stderr.write = logger.error
sys.stdout.write = logger.info