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   "source": [
    "# Print metadata of a GPM file downloaded from NASA\n",
    "from osgeo import gdal\n",
    "import urllib.request\n",
    "import pandas as pd\n",
    "import ipywidgets as widgets\n",
    "\n",
    "BASE_URL = 'https://swatshare.rcac.purdue.edu/temp/MOD16A2.A2014001.'\n",
    "GPM_FILES = ['h00v10.105.2015034090805.hdf', 'h00v09.105.2015034090749.hdf', 'h00v08.105.2015034090734.hdf']\n",
    "\n",
    "def download_and_show_meta(filename):\n",
    "    # download data\n",
    "    url = BASE_URL + filename\n",
    "    print('URL: ', url)\n",
    "    tmpfile = 'data.hdf'\n",
    "    urllib.request.urlretrieve(url, tmpfile)\n",
    "\n",
    "    # Read the downloaded hdf file\n",
    "    hdf = gdal.Open(tmpfile, gdal.GA_ReadOnly)\n",
    "    metadata = hdf.GetMetadata()\n",
    "\n",
    "    # Print Metadata\n",
    "    print(pd.DataFrame(list(metadata.items())))\n",
    "\n",
    "# Label\n",
    "lb=widgets.Label(value=\"Select a filename, then click [Show Meta] button\")\n",
    "display(lb)\n",
    "\n",
    "# selector\n",
    "selector = widgets.Select(\n",
    "    options=GPM_FILES,\n",
    "    value=GPM_FILES[0],    \n",
    ")\n",
    "\n",
    "# button\n",
    "btn = widgets.Button(\n",
    "    description='Show Meta'\n",
    ")\n",
    "display(selector, btn)\n",
    "\n",
    "# Event Handler for the button\n",
    "def on_button_clicked(b):\n",
    "    download_and_show_meta(selector.value)\n",
    "    \n",
    "btn.on_click(on_button_clicked)"
   ]
  }
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