{
 "cells": [
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "# logging 模块：记录日志"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "`logging` 模块可以用来记录日志："
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 1,
   "metadata": {
    "collapsed": true
   },
   "outputs": [],
   "source": [
    "import logging"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "`logging` 的日志类型有以下几种：\n",
    "\n",
    "- `logging.critical(msg)`\n",
    "- `logging.error(msg)`\n",
    "- `logging.warning(msg)`\n",
    "- `logging.info(msg)`\n",
    "- `logging.debug(msg)`\n",
    "\n",
    "级别排序为：`CRITICAL > ERROR > WARNING > INFO > DEBUG > NOTSET`\n",
    "\n",
    "默认情况下，`logging` 的日志级别为 `WARNING`，只有不低于 `WARNING` 级别的日志才会显示在命令行。"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 2,
   "metadata": {
    "collapsed": false
   },
   "outputs": [
    {
     "name": "stderr",
     "output_type": "stream",
     "text": [
      "CRITICAL:root:This is critical message\n",
      "ERROR:root:This is error message\n",
      "WARNING:root:This is warning message\n"
     ]
    }
   ],
   "source": [
    "logging.critical('This is critical message')\n",
    "logging.error('This is error message')\n",
    "logging.warning('This is warning message')\n",
    "\n",
    "# 不会显示\n",
    "logging.info('This is info message')\n",
    "logging.debug('This is debug message')"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "可以这样修改默认的日志级别："
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 3,
   "metadata": {
    "collapsed": false
   },
   "outputs": [
    {
     "name": "stderr",
     "output_type": "stream",
     "text": [
      "INFO:root:This is info message\n"
     ]
    }
   ],
   "source": [
    "logging.root.setLevel(level=logging.INFO)\n",
    "\n",
    "logging.info('This is info message')"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "可以通过 `logging.basicConfig()` 函数来改变默认的日志显示方式："
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 4,
   "metadata": {
    "collapsed": false
   },
   "outputs": [
    {
     "name": "stderr",
     "output_type": "stream",
     "text": [
      "CRITICAL:this program:This is critical message\n"
     ]
    }
   ],
   "source": [
    "logging.basicConfig(format='%(asctime)s: %(levelname)s: %(message)s')\n",
    "\n",
    "logger = logging.getLogger(\"this program\")\n",
    "\n",
    "logger.critical('This is critical message')"
   ]
  }
 ],
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