05-advanced-python/05.01-overview-of-the-sys-module.ipynb

{
 "cells": [
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "# sys 模块简介"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 1,
   "metadata": {
    "collapsed": true
   },
   "outputs": [],
   "source": [
    "import sys"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "## 命令行参数"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "`sys.argv` 显示传入的参数："
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 2,
   "metadata": {
    "collapsed": false
   },
   "outputs": [
    {
     "name": "stdout",
     "output_type": "stream",
     "text": [
      "Writing print_args.py\n"
     ]
    }
   ],
   "source": [
    "%%writefile print_args.py\n",
    "import sys\n",
    "print sys.argv"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "运行这个程序："
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 3,
   "metadata": {
    "collapsed": false
   },
   "outputs": [
    {
     "name": "stdout",
     "output_type": "stream",
     "text": [
      "['print_args.py', '1', 'foo']\n"
     ]
    }
   ],
   "source": [
    "%run print_args.py 1 foo"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "第一个参数 （`sys.args[0]`） 表示的始终是执行的文件名，然后依次显示传入的参数。\n",
    "\n",
    "删除刚才生成的文件："
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 4,
   "metadata": {
    "collapsed": true
   },
   "outputs": [],
   "source": [
    "import os\n",
    "os.remove('print_args.py')"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "## 异常消息"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "`sys.exc_info()` 可以显示 `Exception` 的信息，返回一个 `(type, value, traceback)` 组成的三元组，可以与 `try/catch` 块一起使用： "
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 5,
   "metadata": {
    "collapsed": false
   },
   "outputs": [
    {
     "name": "stdout",
     "output_type": "stream",
     "text": [
      "(<type 'exceptions.ZeroDivisionError'>, ZeroDivisionError('integer division or modulo by zero',), <traceback object at 0x0000000003C6FA08>)\n"
     ]
    }
   ],
   "source": [
    "try:\n",
    "    x = 1/0\n",
    "except Exception:\n",
    "    print sys.exc_info()"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "`sys.exc_clear()` 用于清除所有的异常消息。"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "## 标准输入输出流"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "- sys.stdin\n",
    "- sys.stdout\n",
    "- sys.stderr"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "## 退出Python"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "`sys.exit(arg=0)` 用于退出 Python。`0` 或者 `None` 表示正常退出，其他值表示异常。"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "## Python Path"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "`sys.path` 表示 Python 搜索模块的路径和查找顺序："
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 6,
   "metadata": {
    "collapsed": false
   },
   "outputs": [
    {
     "data": {
      "text/plain": [
       "['',\n",
       " 'C:\\\\Anaconda\\\\python27.zip',\n",
       " 'C:\\\\Anaconda\\\\DLLs',\n",
       " 'C:\\\\Anaconda\\\\lib',\n",
       " 'C:\\\\Anaconda\\\\lib\\\\plat-win',\n",
       " 'C:\\\\Anaconda\\\\lib\\\\lib-tk',\n",
       " 'C:\\\\Anaconda',\n",
       " 'C:\\\\Anaconda\\\\lib\\\\site-packages',\n",
       " 'C:\\\\Anaconda\\\\lib\\\\site-packages\\\\Sphinx-1.3.1-py2.7.egg',\n",
       " 'C:\\\\Anaconda\\\\lib\\\\site-packages\\\\cryptography-0.9.1-py2.7-win-amd64.egg',\n",
       " 'C:\\\\Anaconda\\\\lib\\\\site-packages\\\\win32',\n",
       " 'C:\\\\Anaconda\\\\lib\\\\site-packages\\\\win32\\\\lib',\n",
       " 'C:\\\\Anaconda\\\\lib\\\\site-packages\\\\Pythonwin',\n",
       " 'C:\\\\Anaconda\\\\lib\\\\site-packages\\\\setuptools-17.1.1-py2.7.egg',\n",
       " 'C:\\\\Anaconda\\\\lib\\\\site-packages\\\\IPython\\\\extensions']"
      ]
     },
     "execution_count": 6,
     "metadata": {},
     "output_type": "execute_result"
    }
   ],
   "source": [
    "sys.path"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "在程序中可以修改，添加新的路径。"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "## 操作系统信息"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "`sys.platform` 显示当前操作系统信息：\n",
    "\n",
    "- `Windows: win32`\n",
    "- `Mac OSX: darwin`\n",
    "- `Linux:   linux2`"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 7,
   "metadata": {
    "collapsed": false
   },
   "outputs": [
    {
     "data": {
      "text/plain": [
       "'win32'"
      ]
     },
     "execution_count": 7,
     "metadata": {},
     "output_type": "execute_result"
    }
   ],
   "source": [
    "sys.platform"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "返回 `Windows` 操作系统的版本："
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 8,
   "metadata": {
    "collapsed": false
   },
   "outputs": [
    {
     "data": {
      "text/plain": [
       "sys.getwindowsversion(major=6, minor=2, build=9200, platform=2, service_pack='')"
      ]
     },
     "execution_count": 8,
     "metadata": {},
     "output_type": "execute_result"
    }
   ],
   "source": [
    "sys.getwindowsversion()"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "标准库中有 `planform` 模块提供更详细的信息。"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "## Python 版本信息"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 9,
   "metadata": {
    "collapsed": false
   },
   "outputs": [
    {
     "data": {
      "text/plain": [
       "'2.7.10 |Anaconda 2.3.0 (64-bit)| (default, May 28 2015, 16:44:52) [MSC v.1500 64 bit (AMD64)]'"
      ]
     },
     "execution_count": 9,
     "metadata": {},
     "output_type": "execute_result"
    }
   ],
   "source": [
    "sys.version"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 10,
   "metadata": {
    "collapsed": false
   },
   "outputs": [
    {
     "data": {
      "text/plain": [
       "sys.version_info(major=2, minor=7, micro=10, releaselevel='final', serial=0)"
      ]
     },
     "execution_count": 10,
     "metadata": {},
     "output_type": "execute_result"
    }
   ],
   "source": [
    "sys.version_info"
   ]
  }
 ],
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   "display_name": "Python 2",
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   "codemirror_mode": {
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