python的日志模块 logging

python 的日志用起来很简单：
主要牵涉到3个模块：

• logging

• logging.config

• logging.handles

5个日志等级：

DEBUG	Detailed information, typically of interest only when diagnosing problems.
INFO	Confirmation that things are working as expected.
WARNING	An indication that something unexpected happened, or indicative of some problem in the near future (e.g. ‘disk space low’). The software is still working as expected.
ERROR	Due to a more serious problem, the software has not been able to perform some function.
CRITICAL	A serious error, indicating that the program itself may be unable to continue running.

默认的是 WARNING

例子1：
import logging logging.warning('Watch out!') #会打印到控制台
logging.info('I told you so') # 什么也不打印

输出为：
WARNING:root:Watch out!

例子2：输出日志到文件
import logging logging.basicConfig(filename='example.log',level=logging.DEBUG) logging.debug('This message should go to the log file') logging.info('So should this') logging.warning('And this, too')
输出为（文件example.log的内容）：
DEBUG:root:This message should go to the log file INFO:root:So should this WARNING:root:And this, too

例子3：日志大小/文件数设置
import logging
import logging.handlers
import glob

LOG_FILENAME = 'logging_rotatingfile_example.out'
# Set up a specific logger with our desired output level
my_logger = logging.getLogger('MyLogger')
my_logger.setLevel(logging.DEBUG)

# Add the log message handler to the logger
handler = logging.handlers.RotatingFileHandler(
              LOG_FILENAME, maxBytes=20, backupCount=5)
my_logger.addHandler(handler)
# Log some messages
for i in range(20):
    my_logger.debug('i = %d' % i)
# See what files are created
logfiles = glob.glob('%s*' % LOG_FILENAME)
for filename in logfiles:
    print(filename)

上面例子设置了单个日志最大文件大小20Byte，备份文件数为5个，也就时当前日志一个文件，和5个备份文件

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下一篇介绍logging日志格式的设定。。。