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   "source": [
    "## 02. Fetching binary data with `urllib` and unzipping files with `zipfile`\n",
    "\n",
    "If you can get the web address, or URL, of a specific binary file that you found on some website, you can usually download it fairly easily using Python's native `urllib` package, which is a simple interface for interacting with network resources. \n",
    "\n",
    "Here, we demonstrate how to use the `request` sub-module of `urllib` package to send a request to a server and handle the repsonse. While `request` can do much more than just download files, we'll keep ourselves to its `request.urlretrieve` function, which is designed to fetch remote files, saving them as local files.. \n",
    "\n",
    "We'll use the urllib.urlretrive to download a Census tract shapefile located on the US Census's web server: https://www2.census.gov/geo/tiger/TIGER2017/TRACT. The one file we'll get is tracts for North Dakota (because it's a fairly small file): `tl_2017_38_tract.zip`. \n",
    "\n",
    "We'll also take this opportunity to examine how Python can unzip files with the `zipfile` library."
   ]
  },
  {
   "cell_type": "code",
   "execution_count": null,
   "metadata": {},
   "outputs": [],
   "source": [
    "#Import the two modules\n",
    "from urllib import request\n",
    "import zipfile"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": null,
   "metadata": {},
   "outputs": [],
   "source": [
    "#Specify the URL of the resource\n",
    "theURL = 'https://www2.census.gov/geo/tiger/TIGER2017/TRACT/tl_2017_38_tract.zip'"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": null,
   "metadata": {},
   "outputs": [],
   "source": [
    "#Set a local filename to save the file as\n",
    "localFile = 'tl_2017_38_tract.zip'"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": null,
   "metadata": {},
   "outputs": [],
   "source": [
    "#The urlretrieve function downloads a file, saving it as the file name we specify\n",
    "request.urlretrieve(url=theURL,filename=localFile)"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "Now take a look at the contents of your folder. You'll see a local copy of the zip file!"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": null,
   "metadata": {},
   "outputs": [],
   "source": [
    "!dir *.zip"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "This works for images too..."
   ]
  },
  {
   "cell_type": "code",
   "execution_count": null,
   "metadata": {},
   "outputs": [],
   "source": [
    "imgURL = 'https://imgs.xkcd.com/comics/state_borders.png'\n",
    "request.urlretrieve(url=imgURL,filename=\"map.jpg\",);"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": null,
   "metadata": {
    "scrolled": true
   },
   "outputs": [],
   "source": [
    "#Display the file in our notebook\n",
    "from IPython.display import Image\n",
    "Image(\"map.jpg\")"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "So now, let's look at how the zipfile module can unzip it"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": null,
   "metadata": {},
   "outputs": [],
   "source": [
    "#First open the local zip file as a zipFile object\n",
    "zipObject = zipfile.ZipFile(localFile)"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": null,
   "metadata": {},
   "outputs": [],
   "source": [
    "#Create a folder to hold the file\n",
    "\n",
    "#Name the folder we'll create the same as the file, without the extension\n",
    "outFolderName = localFile[:-4]\n",
    "\n",
    "#Well us the os module to do check if the folder exists, and create if not\n",
    "import os\n",
    "if not os.path.exists(outFolderName): \n",
    "    outFolder = os.mkdir(localFile[:-4])"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": null,
   "metadata": {},
   "outputs": [],
   "source": [
    "zipObject.extractall(path=outFolderName)\n",
    "zipObject.close()"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "And viola! If we use some looping, we can tell Python to download a lot of files at our command!"
   ]
  }
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