这里有两个例子，一个打印日志(stdout)，另一个将日志写入文件:

import logging
import sys

logger = logging.getLogger()
logger.setLevel(logging.INFO)
formatter = logging.Formatter('%(asctime)s | %(levelname)s | %(message)s')

stdout_handler = logging.StreamHandler(sys.stdout)
stdout_handler.setLevel(logging.DEBUG)
stdout_handler.setFormatter(formatter)

file_handler = logging.FileHandler('logs.log')
file_handler.setLevel(logging.DEBUG)
file_handler.setFormatter(formatter)


logger.addHandler(file_handler)
logger.addHandler(stdout_handler)

在这个示例中，所有日志都将被打印出来，并被写入一个名为logs.log的文件

使用的例子:

logger.info('This is a log message!')
logger.error('This is an error message.')

所有内置日志处理程序的列表https://docs.python.org/3/library/logging.handlers.html

一个使用日志记录的例子。使用basicConfig而不是logging.fileHandler()

logging.basicConfig(filename=logname,
                    filemode='a',
                    format='%(asctime)s,%(msecs)d %(name)s %(levelname)s %(message)s',
                    datefmt='%H:%M:%S',
                    level=logging.DEBUG)

logging.info("Running Urban Planning")

logger = logging.getLogger('urbanGUI')

按顺序，这五个部分做以下工作:

设置输出文件(filename=logname) 将其设置为追加而不是覆盖(filemode='a') 确定输出消息的格式(format=…) 确定输出时间的格式(datefmt='%H:%M:%S') 并确定它将接受的最小消息级别(level=logging.DEBUG)。

import logging

from datetime import datetime

filename = datetime.now().strftime("%d-%m-%Y %H-%M-%S")#Setting the filename from current date and time
logging.basicConfig(filename=filename, filemode='a',
                    format="%(asctime)s, %(msecs)d %(name)s %(levelname)s [ %(filename)s-%(module)s-%(lineno)d ]  : %(message)s",
                    datefmt="%H:%M:%S",
                    level=logging.DEBUG)

asctime %(asctime)s Human-readable time when the LogRecord was created. By default this is of the form ‘2003-07-08 16:49:45,896’ (the numbers after the comma are millisecond portion of the time). created %(created)f Time when the LogRecord was created (as returned by time.time()). exc_info You shouldn’t need to format this yourself. Exception tuple (à la sys.exc_info) or, if no exception has occurred, None. filename %(filename)s Filename portion of pathname. funcName %(funcName)s Name of function containing the logging call. levelname %(levelname)s Text logging level for the message ('DEBUG', 'INFO', 'WARNING', 'ERROR', 'CRITICAL'). levelno %(levelno)s Numeric logging level for the message (DEBUG, INFO, WARNING, ERROR, CRITICAL). lineno %(lineno)d Source line number where the logging call was issued (if available). message %(message)s The logged message, computed as msg % args. This is set when Formatter.format() is invoked. module %(module)s Module (name portion of filename). msecs %(msecs)d Millisecond portion of the time when the LogRecord was created. msg You shouldn’t need to format this yourself. The format string passed in the original logging call. Merged with args to produce message, or an arbitrary object (see Using arbitrary objects as messages). name %(name)s Name of the logger used to log the call. pathname %(pathname)s Full pathname of the source file where the logging call was issued (if available). process %(process)d Process ID (if available). processName %(processName)s Process name (if available). relativeCreated %(relativeCreated)d Time in milliseconds when the LogRecord was created, relative to the time the logging module was loaded. stack_info You shouldn’t need to format this yourself. Stack frame information (where available) from the bottom of the stack in the current thread, up to and including the stack frame of the logging call which resulted in the creation of this record. thread %(thread)d Thread ID (if available). threadName %(threadName)s Thread name (if available).

有关日志记录的更多信息，请转到python3官方页面。

这里有一个更简单的方法。这个解决方案不使用a Config字典，并使用一个旋转文件处理程序，如下所示:

import logging
from logging.handlers import RotatingFileHandler
     
logging.basicConfig(handlers=[RotatingFileHandler(filename=logpath+filename,
                     mode='w', maxBytes=512000, backupCount=4)], level=debug_level,
                     format='%(levelname)s %(asctime)s %(message)s', 
                    datefmt='%m/%d/%Y%I:%M:%S %p')
     
logger = logging.getLogger('my_logger')

或像这样:

import logging
from logging.handlers import RotatingFileHandler
     
handlers = [ RotatingFileHandler(filename=logpath+filename, 
            mode='w', 
            maxBytes=512000, 
            backupCount=4)
           ]
logging.basicConfig(handlers=handlers, 
                    level=debug_level, 
                    format='%(levelname)s %(asctime)s %(message)s', 
                    datefmt='%m/%d/%Y%I:%M:%S %p')
     
logger = logging.getLogger('my_logger')

handlers变量需要是一个可迭代对象。Logpath +filename和debug_level只是变量 各自的信息。当然，函数参数的值是向上的 给你。

第一次我使用日志模块，我犯了写下面的错误，这产生了一个操作系统文件锁错误(的 以上是解决方案):

import logging
from logging.handlers import RotatingFileHandler
     
logging.basicConfig(filename=logpath+filename, 
       level=debug_level, 
       format='%(levelname)s %(asctime)s %(message)s', 
       datefmt='%m/%d/%Y%I:%M:%S %p')
     
logger = logging.getLogger('my_logger')
logger.addHandler(RotatingFileHandler(
       filename=logpath+filename, 
       mode='w', 
       maxBytes=512000, 
       backupCount=4))

摘自“伐木食谱”:

# create logger with 'spam_application'
logger = logging.getLogger('spam_application')
logger.setLevel(logging.DEBUG)
# create file handler which logs even debug messages
fh = logging.FileHandler('spam.log')
fh.setLevel(logging.DEBUG)
logger.addHandler(fh)

你可以开始了。

附注:一定要阅读日志指南。

import sys
import logging

from util import reducer_logfile
logging.basicConfig(filename=reducer_logfile, format='%(message)s',
                    level=logging.INFO, filemode='w')