Python开发【杂货铺】：模块logging

logging模块　

很多程序都有记录日志的需求，并且日志中包含的信息即有正常的程序访问日志，还可能有错误、警告等信息输出，python的logging模块提供了标准的日志接口，你可以通过它存储各种格式的日志，logging的日志可以分为 debug、info、warning、error、critical 5个级别，下面我们看一下怎么用。默认情况下日志级别为warning，只有大于warning的日志才会打印。

模块初识：

#logging初识

import logging

logging.warning("user [James] attempted wrong password more than 3 times")
logging.critical("server is down")

# WARNING:root:user [James] attempted wrong password more than 3 times
# CRITICAL:root:server is down

上面的代码是最简单的方式，括号里的内容为打印的信息，logging.后的方法为日志的级别，下面看看logging五个级别的详细信息

如果想把日志写到文件里，也很简单：

#日志打印到文件中

import  logging

logging.basicConfig(filename="example.log",level=logging.INFO,
                    format="%(asctime)s  [%(filename)s:%(lineno)d] %(message)s", datefmt="%m/%d/%Y %H:%M:%S [%A]")
                                                                # H 24小时格式  I 12小时格式  A 周几完整  a 周几简写  p AM/PM

logging.debug("This message should go to the log file")
logging.info("So should this")
logging.warning("And this ,too")

logging.basicConfig里定义了输入文件路径，输入日志信息的级别，输入的格式，格式可自定义；执行完代码后example.log文件会生成信息如下：

10/31/2016 17:16:17 [Monday] So should this
10/31/2016 17:16:17 [Monday] And this ,too

其中下面这句中的level=loggin.INFO意思是，把日志纪录级别设置为INFO，也就是说，只有比日志是INFO或比INFO级别更高的日志才会被纪录到文件里，在这个例子， 第一条日志是不会被纪录的，如果希望纪录debug的日志，那把日志级别改成DEBUG就行了

如果想同时把log打印在屏幕和文件日志里，就需要了解一点复杂的知识了：

The logging library takes a modular approach and offers several categories of components: loggers, handlers, filters, and formatters.

• Loggers expose the interface that application code directly uses.
• Handlers send the log records (created by loggers) to the appropriate destination.
• Filters provide a finer grained facility for determining which log records to output.
• Formatters specify the layout of log records in the final output.

#!/usr/bin/env python
# -*- coding:utf-8 -*-
#-Author-Lian

import  logging

#创建logger
logger = logging.getLogger("test_log")  #创建logger对象   括号内容随便写
logger.setLevel(logging.INFO)       #全局日志级别

ch = logging.StreamHandler()        #日志打印到屏幕上
ch.setLevel(logging.DEBUG)          #指定ch日志打印级别

fh = logging.FileHandler("access.log")      #日志存进文件
fh.setLevel(logging.WARNING)            #指定fh日志输入级别

formatter = logging.Formatter("%(asctime)s - %(name)s - %(levelname)s - %(message)s")   #定义日志格式，可写多个

#添加日志格式到ch,fh
ch.setFormatter(formatter)
fh.setFormatter(formatter)

#添加ch,fh到logger中
logger.addHandler(ch)
logger.addHandler(fh)

logger.debug('debug message')
logger.info('info message')
logger.warn('warn message')
logger.error('error message')
logger.critical('critical message')

全局日志级别为整个程序的底线，局部日志级别要想打印则不能比这个级别再低了

屏幕打印信息：

2016-10-31 17:23:42,988 - test_log - INFO - info message
2016-10-31 17:23:42,988 - test_log - WARNING - warn message
2016-10-31 17:23:42,988 - test_log - ERROR - error message
2016-10-31 17:23:42,988 - test_log - CRITICAL - critical message

access.log:

2016-10-31 17:02:06,223 - test_log - WARNING - warn message
2016-10-31 17:02:06,224 - test_log - ERROR - error message
2016-10-31 17:02:06,224 - test_log - CRITICAL - critical message

日志所有的格式：

重要的几个格式：%(lineno)d 输出打印日志代码行 ，%(process)d输出打印日志的进程ID ，%(thread)d输出打印日志的线程ID

日志实例：http://www.cnblogs.com/lianzhilei/p/6513230.html

生产应用（屏幕打印，日志文件写入）：

import logging
from logging.handlers import RotatingFileHandler

handler = RotatingFileHandler('test.log', maxBytes=20*1024*1024, backupCount=200,encoding='utf-8')
handler.setLevel(logging.INFO)
formatter = logging.Formatter('[%(asctime)s] [%(filename)s:%(lineno)d] %(levelname)s %(message)s')
handler.setFormatter(formatter)
logging.basicConfig(datefmt='%Y-%m-%d %H:%M:%S', level=logging.DEBUG)
logger = logging.getLogger()
logger.addHandler(handler)

logger.debug('debug message')
logger.info('info message')
logger.warn('warn message')
logger.error('error message')
logger.critical('critical message')

生产应用（多进程下日志记录）：

from cloghandler import ConcurrentRotatingFileHandler

rotateHandler = ConcurrentRotatingFileHandler(logConfig['filePath'], "a", 20 * 1024 * 1024, 200)
rotateHandler.setLevel(logging.INFO)
formatter = logging.Formatter('[%(asctime)s] [process:%(process)s] [%(filename)s:%(lineno)d]  %(levelname)s %(message)s')
rotateHandler.setFormatter(formatter)
log = logging.getLogger()
log.addHandler(rotateHandler)
log.setLevel(logging.INFO)

模块安装：

pip install ConcurrentLogHandler

　

import logging

try:
    11 +a
except Exception as e:
    # logging.error("user [James] attempted wrong password more than 3 times")
    logging.error("user [James] attempted wrong password more than 3 times",exc_info=True)

# ERROR:root:user [James] attempted wrong password more than 3 times
# Traceback (most recent call last):
#   File "Z:/workbanch/move_file.py", line 10, in <module>
#     11 +a
# NameError: name 'a' is not defined