{
 "cells": [
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "Numpy能从磁盘直接存储和加载数据，不论是文本格式还是二进制模式。这里我们只考虑Numpy的二进制模式，因为大多数用户更喜欢用pandas或其他工具来加载text或tabular数据。\n",
    "\n",
    "np.save和np.load。数组会以未压缩的原始二进制模式被保存，后缀为.npy:"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 3,
   "metadata": {
    "collapsed": false
   },
   "outputs": [],
   "source": [
    "import numpy as np\n",
    "\n",
    "arr = np.arange(10)\n",
    "np.save('../examples/some_array', arr)"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "即使保存的时候没有加后缀，也会被自动加上。可以用np.load来加载数组："
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 6,
   "metadata": {
    "collapsed": false
   },
   "outputs": [
    {
     "data": {
      "text/plain": [
       "array([0, 1, 2, 3, 4, 5, 6, 7, 8, 9])"
      ]
     },
     "execution_count": 6,
     "metadata": {},
     "output_type": "execute_result"
    }
   ],
   "source": [
    "np.load('../examples/some_array.npy')"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "用np.savez能保存多个数组，还可以指定数组对应的关键字，不过是未压缩的npz格式："
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 7,
   "metadata": {
    "collapsed": true
   },
   "outputs": [],
   "source": [
    "np.savez('../examples/array_archive.npz', a=arr, b=arr)"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "加载.npz文件的时候，得到一个dict object："
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 9,
   "metadata": {
    "collapsed": false
   },
   "outputs": [
    {
     "data": {
      "text/plain": [
       "array([0, 1, 2, 3, 4, 5, 6, 7, 8, 9])"
      ]
     },
     "execution_count": 9,
     "metadata": {},
     "output_type": "execute_result"
    }
   ],
   "source": [
    "arch = np.load('../examples/array_archive.npz')\n",
    "arch['b']"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "可以用np.savez_compressed来压缩文件："
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 10,
   "metadata": {
    "collapsed": true
   },
   "outputs": [],
   "source": [
    "np.savez_compressed('../examples/array_compressed.npz', a=arr, b=arr)"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": null,
   "metadata": {
    "collapsed": true
   },
   "outputs": [],
   "source": []
  }
 ],
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