[Python3] 042 log

LOG

• logging module logs module level function
• It includes four components

1. Log concepts

1.1 log level level

1. DEBUG
2. INFO
3. NOTICE
4. WARNING
5. ERROR
6. CRITICAL
7. ALERT
8. EMERGENCY

• Users can program the information they need attention

1.2 LOG role of

• debugging
• Understand the operation of the software
• Analysis of Orientation

1.3 log

• time
• level
• location
• content

1.4 mature third-party log

• logging
• Log4j
• log4php

1.5 Note

• Do not operate frequently IO

2. Logging Module

2.1 log level

• DEBUG
• INFO
• WARNING
• ERROR
• CRITICAL

2.2 Use

1. Direct use of logging, logging because the other components of the package

2. Four custom components directly with loging

2.3 Notes

• Initialize or write log instances need to specify the level
• Level can be customized
• Only when the level is equal to or higher than the specified level was only recorded

2.4 logging module level log

2.4.1 logging of several functions

function	DEFINITIONS
logging.debug(msg, *args, **kwargs)	Create a severity level DEBUG logging
logging.info(msg, *args, **kwargs)	Create a severity level of INFO logging
logging.warning(msg, *args, **kwargs)	Create a severity level WARNING logging
logging.error(msg, *args, **kwargs)	Create a severity level ERROR logging
logging.critical(msg, *args, **kwargs)	Create a severity level CRITICAL logging
logging.log(level, *args, **kwargs)	Create a severity level for the level of logging
logging.basicConfig(**kwargs)	To root logger a one-time configuration

• logging.basicConfig(**kwargs)
  • Only when the first call to act
  • Do not configure the default value logger
    • Output: sys.stderr
    • Level: WARNING
    • Format: level: log_name: content

2.4 Example 2

• format parameters

parameter	usage	DEFINITIONS
asctime	%(asctime)s	Time log of events - human-readable time such as: 2019-12-2417: 00: 12,765
created	%(created)f	Time log of events - the time stamp and calling time.time value returned by the function () the same
relativeCreated	%(relativeCreated)d	Log event time with respect to the relative number of milliseconds logging module load time
msecs	%(msecs)d	Log event millisecond section of the event
levelname	%(levelname)s	Log level text form of the log record 'DEBUG', 'INFO', 'WARNING', 'ERROR', 'CRITICAL'
levelno	%(levelno)s	The digital form of the log record log level (10, 20, 30, 40, 50)
name	%(name)s	Log name used, the default is the 'root' as the default rootLogger
message	%(message)s	Text logging, calculation obtained by msg% args
pathname	%(pathname)s	The full path to the source file is called logging function
filename	%(filename)s	Pathname of the file name, including file suffix
module	%(module)s	filename part of the name, does not contain a suffix
lineno	%(lineno)d	The line number to call log function of the source code resides
funcName	%(funcName)s	Call logging function name function
process	%(process)d	Process ID
processName	%(processName)s	Process name, Python 3.1 new
thread	%(thread)d	Thread ID
threadName	%(thread)s	Thread name

2.5 logging process flow module

• Four components

Package	effect
Logger Logger	Generating a log of the interface
Processor Handler	Sends the generated log to the corresponding destination
Filters Filter	Those finer control log output
Formatter Formatter	Formatting the output information

2.5.1 Logger

• Produce a log

function	DEFINITIONS
Logger.setLevel ()	Minimum level of severity set logger will be processed log messages
Logger.addHandler () 和 Logger.removeHandler ()	Logger objects for adding and removing a handler objects
Logger.addFilter () 和 Logger.removeFilter ()	Logger objects for adding and removing a filter objects
Logger.debug	产生一条 debug 级别的日志 info, error 等同理
Logger.exception()	创建类似于 Logger.error 的日志消息
Logger.log()	获取一个明确的日志 level 参数类创建一个日志记录

• 如何得到一个 logger 对象

1. 实例化
2. logging.getLogger()

2.5.2 Handler

• 把 log 发送到制定位置
• 方法
  • setLevel
  • setFormat
  • addFilter, removeFilter
• 不需要直接使用，Handler 是基类

方法	释义
logging.StreamHandler	将日志消息发送到输出到 Stream 如 std.out, std.err 或任何 file-like 对象
logging.FileHandler	将日志消息发送到磁盘文件 默认情况下文件大小会无限增长
logging.handlers.RotatingFileHandler	将日志消息发送到磁盘文件，并支持日志文件按大小切割
logging.hanlders.TimedRotatingFileHandler	将日志消息发送到磁盘文件，并支持日志文件按时间切割
logging.handlers.HTTPHandler	将日志消息以 GET 或 POST 的方式发送给一个 HTTP 服务器
logging.handlers.SMTPHandler	将日志消息发送给一个指定的 email 地址
logging.NullHandler	该 Handler 实例会忽略 error messages 通常被想使用 logging 的 library 开发者使用来避免 'No handlers could be found for logger XXX' 信息的出现

2.5.3 Filter 类

• 可以被 Handler 和 Logger 使用
• 控制传递过来的信息的具体内容

2.5.4 Format 类

• 直接实例化
• 可以继承 Format 添加特殊内容
• 三个参数

参数	释义
fmt	指定消息格式化字符串，如果不指定该参数则默认使用 message 的原始值
datefmt	指定日期格式字符串，如果不指定该参数则默认使用 "%Y-%m-%d %H:%M:%S"
style	Python 3.2 时新增的参数，可取值为 '%', '{' 和 '$'，如果不指定该参数则默认使用 '%'