log日志

在写代码开发期间，往往会涉及到打印Log日志。

在此总结log相关的内容。

日志 == log == Logger == logging

用来打印日志输出信息用于调试。

log的等级

log日志有一些常见的登记，最基本的几种有：

• info: 用于输出一些阶段性的告知用户的信息，比如用户已成功登录之类的
• debug: 用于调试目的，而输出一些信息，比如打印某些变量的值
• warn/warning: 用于输出一些不正常的情况，需要引起用户注意了，比如app检测存储空间快满了
• error: 显示一些错误级别的信息，往往意味着程序也要终止运行了。需要用户处理错误，或者退出程序之类的

其他不是很常见的几种：

• finest/fine：表示程序正常级别输出的信息
• trace: 类似于debug，用于输出一些追踪调试信息
• verbose：事无巨细的，最详尽的信息
• severe：严重的问题，类似于error
• critical：关键的问题，类似于severe

log相关的库

log4xxx系列

有个通用的log的库：log4xxx

针对于不同语言的log4xxx分别是：

• Java语言：Log4j
  • log4j
  • 新版本：Log4j – Log4j 2 Guide - Apache Log4j 2
• C语言：log4c
  • log4c
• Go语言：log4go
  • alecthomas/log4go: Logging package similar to log4j for the Go programming language
• 微软的.NET框架（C#等语言）：log4net
  • Open Source Logging Tools in C#
• Delphi语言：Log4Delphi
  • Welcome to Log4Delphi
• C++: log4cpp
  • 其他相关：
    • log4cplus
    • log4cxx

Python

Python的log库：自带的库logging

自己也整理和封装成基本的函数：

def loggingInit(filename = None,
                fileLogLevel = logging.DEBUG,
                fileLogFormat = '%(asctime)s LINE %(lineno)-4d %(levelname)-7s %(message)s',
                fileLogDateFormat = '%Y/%m/%d %I:%M:%S',
                enableConsole = True,
                consoleLogLevel = logging.INFO,
                consoleLogFormat = "%(asctime)s LINE %(lineno)-4d %(levelname)-7s %(message)s",
                consoleLogDateFormat = '%Y/%m/%d %I:%M:%S',
                ):
    """
    init logging for both log to file and console
    :param logFilename: input log file name
        if not passed, use current script filename
    :return: none
    """
    logFilename = ""
    if filename:
        logFilename = filename
    else:
        logFilename = getInputFileBasenameNoSuffix() + ".log"

    logging.basicConfig(
                    level    = fileLogLevel,
                    format   = fileLogFormat,
                    datefmt  = fileLogDateFormat,
                    filename = logFilename,
                    filemode = 'w')
    if enableConsole :
        # define a Handler which writes INFO messages or higher to the sys.stderr
        console = logging.StreamHandler()
        console.setLevel(consoleLogLevel)
        # set a format which is simpler for console use
        formatter = logging.Formatter(fmt=consoleLogFormat, datefmt=consoleLogDateFormat)
        # tell the handler to use this format
        console.setFormatter(formatter)
        logging.getLogger('').addHandler(console)

详见： https://github.com/crifan/crifanLib/blob/master/python/crifanLib.py

Flask

Python的Flask中也可以打印log

对应的代码： config.py

############################################################
# File Log
############################################################
LOG_FILE_FILENAME = "logs/sipevents.log"

LOG_FILE_FORMAT = "[%(asctime)s %(levelname)s %(filename)s:%(lineno)d %(funcName)s] %(message)s"

__init__.py

import logging
from logging.handlers import RotatingFileHandler

fileHandler = RotatingFileHandler(
    app.config['LOG_FILE_FILENAME'],
    maxBytes = 2*1024*1024,
    backupCount = 3,
    encoding = "UTF-8")
fileHandler.setLevel(logging.DEBUG)

fileLogFormatterStr = app.config["LOG_FILE_FORMAT"]
fileLogFormatter = logging.Formatter(fileLogFormatterStr)
fileHandler.setFormatter(fileLogFormatter)
app.logger.addHandler(fileHandler)

run.py

from sipevents import app

if __name__ == '__main__':
    app.run(debug=True)

输出log的效果是：

[2016-09-02 16:59:25,938 DEBUG views.py:804 creat_event] requestMethod=GET

对应参数的解释是：

更加完整的参数解释是：

Swift

iOS的swift中也遇到过log库：XCGLogger

其中的log的定义是：

    /// Enum defining our log levels
    public enum Level : Int, Comparable, CustomStringConvertible {
        case verbose
        case debug
        case info
        case warning
        case error
        case severe
        case none

        ...
        public var description: String { get }
        public static let all: [XCGLogger.XCGLogger.Level]
    }

和基本的封装

import XCGLogger

func initLog() {
    gLog = XCGLogger.default//XCGLogger.defaultInstance()

    //var logLevel:XCGLogger.LogLevel = XCGLogger.LogLevel.debug

    var logLevel:XCGLogger.Level = XCGLogger.Level.debug
    if LogLevelIsVerbose {
        logLevel = XCGLogger.Level.verbose
    }

    var fileLogLevel:XCGLogger.Level = XCGLogger.Level.debug
    if FileLogLevelIsVerbose {
        fileLogLevel = XCGLogger.Level.verbose
    }

    gLog.setup(
        level: logLevel,
        showThreadName: true,
        showLevel: true,
        showFileNames: true,
        showLineNumbers: true,
        writeToFile: LogFile,
        fileLevel: fileLogLevel)
}

之后即可正常log了：

  gLog.info("UIScreen.mainScreen().bounds=\(UIScreen.main.bounds)")
  gLog.debug("forgetPasswordVC:\(forgetPasswordVC)”)
  gLog.warning("jpush set alias \(alias) failed")
  gLog.error("上传附件失败: \(encodingError)”)