notebooks/multiindex_slice.ipynb

{
 "cells": [
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "# Select all the contents of a MultiIndex level\n",
    "\n",
    "## tl;dr: Use `slice(None)` or `pandas.IndexSlice`\n",
    "\n",
    "`results.loc[(slice(None), slice(None), \"Ballots Cast\"), :]`\n",
    "\n",
    "or\n",
    "\n",
    "`results.loc[pd.IndexSlice[:, :, \"Ballots Cast\"], :]`\n",
    "\n",
    "## Introduction\n",
    "\n",
    "Pandas [`MultiIndex`](https://pandas.pydata.org/pandas-docs/stable/reference/api/pandas.MultiIndex.html) provides a useful way to [select specific values](https://pandas.pydata.org/docs/getting_started/intro_tutorials/03_subset_data.html) in a `DataFrame` when the data is hierarchical. I find myself using `MultiIndex` often when working with election data where a value might be associated with a county, jurisdiction and ultimately precinct.\n",
    "\n",
    "It's intuitive to traverse the hierarchy to get slices of data, but it's a less intuitive when you want to get specific values for the second level of the index, for any value of the first level.\n",
    "\n",
    "The official reference for accessing items in a MultiIndex is the [MultiIndex / advanced indexing](https://pandas.pydata.org/pandas-docs/stable/user_guide/advanced.html) section of the Pandas documentation. "
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 1,
   "metadata": {},
   "outputs": [],
   "source": [
    "# Setup\n",
    "\n",
    "import io\n",
    "\n",
    "import pandas as pd"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "## Load Alcona County, Michigan Election Results\n",
    "\n",
    "This is a subset of data available at https://github.com/openelections/openelections-data-mi/blob/master/2020/20200310__mi__primary__president__alcona__precinct.csv."
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 2,
   "metadata": {},
   "outputs": [
    {
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       "\n",
       "    .dataframe tbody tr th {\n",
       "        vertical-align: top;\n",
       "    }\n",
       "\n",
       "    .dataframe thead th {\n",
       "        text-align: right;\n",
       "    }\n",
       "</style>\n",
       "<table border=\"1\" class=\"dataframe\">\n",
       "  <thead>\n",
       "    <tr style=\"text-align: right;\">\n",
       "      <th></th>\n",
       "      <th>county</th>\n",
       "      <th>precinct</th>\n",
       "      <th>office</th>\n",
       "      <th>district</th>\n",
       "      <th>party</th>\n",
       "      <th>candidates</th>\n",
       "      <th>votes</th>\n",
       "    </tr>\n",
       "  </thead>\n",
       "  <tbody>\n",
       "    <tr>\n",
       "      <th>0</th>\n",
       "      <td>Alcona</td>\n",
       "      <td>Alcona Twp</td>\n",
       "      <td>Registered Voters</td>\n",
       "      <td>NaN</td>\n",
       "      <td>NaN</td>\n",
       "      <td>NaN</td>\n",
       "      <td>975</td>\n",
       "    </tr>\n",
       "    <tr>\n",
       "      <th>1</th>\n",
       "      <td>Alcona</td>\n",
       "      <td>Caledonia Twp</td>\n",
       "      <td>Registered Voters</td>\n",
       "      <td>NaN</td>\n",
       "      <td>NaN</td>\n",
       "      <td>NaN</td>\n",
       "      <td>955</td>\n",
       "    </tr>\n",
       "    <tr>\n",
       "      <th>2</th>\n",
       "      <td>Alcona</td>\n",
       "      <td>Curtis Twp</td>\n",
       "      <td>Registered Voters</td>\n",
       "      <td>NaN</td>\n",
       "      <td>NaN</td>\n",
       "      <td>NaN</td>\n",
       "      <td>1024</td>\n",
       "    </tr>\n",
       "    <tr>\n",
       "      <th>3</th>\n",
       "      <td>Alcona</td>\n",
       "      <td>Greenbush Twp</td>\n",
       "      <td>Registered Voters</td>\n",
       "      <td>NaN</td>\n",
       "      <td>NaN</td>\n",
       "      <td>NaN</td>\n",
       "      <td>1257</td>\n",
       "    </tr>\n",
       "    <tr>\n",
       "      <th>4</th>\n",
       "      <td>Alcona</td>\n",
       "      <td>Gustin Twp</td>\n",
       "      <td>Registered Voters</td>\n",
       "      <td>NaN</td>\n",
       "      <td>NaN</td>\n",
       "      <td>NaN</td>\n",
       "      <td>637</td>\n",
       "    </tr>\n",
       "    <tr>\n",
       "      <th>5</th>\n",
       "      <td>Alcona</td>\n",
       "      <td>Harrisville Twp</td>\n",
       "      <td>Registered Voters</td>\n",
       "      <td>NaN</td>\n",
       "      <td>NaN</td>\n",
       "      <td>NaN</td>\n",
       "      <td>1144</td>\n",
       "    </tr>\n",
       "    <tr>\n",
       "      <th>6</th>\n",
       "      <td>Alcona</td>\n",
       "      <td>Hawes Twp</td>\n",
       "      <td>Registered Voters</td>\n",
       "      <td>NaN</td>\n",
       "      <td>NaN</td>\n",
       "      <td>NaN</td>\n",
       "      <td>943</td>\n",
       "    </tr>\n",
       "    <tr>\n",
       "      <th>7</th>\n",
       "      <td>Alcona</td>\n",
       "      <td>Haynes Twp</td>\n",
       "      <td>Registered Voters</td>\n",
       "      <td>NaN</td>\n",
       "      <td>NaN</td>\n",
       "      <td>NaN</td>\n",
       "      <td>645</td>\n",
       "    </tr>\n",
       "    <tr>\n",
       "      <th>8</th>\n",
       "      <td>Alcona</td>\n",
       "      <td>Mikado Twp</td>\n",
       "      <td>Registered Voters</td>\n",
       "      <td>NaN</td>\n",
       "      <td>NaN</td>\n",
       "      <td>NaN</td>\n",
       "      <td>785</td>\n",
       "    </tr>\n",
       "    <tr>\n",
       "      <th>9</th>\n",
       "      <td>Alcona</td>\n",
       "      <td>Millen Twp</td>\n",
       "      <td>Registered Voters</td>\n",
       "      <td>NaN</td>\n",
       "      <td>NaN</td>\n",
       "      <td>NaN</td>\n",
       "      <td>363</td>\n",
       "    </tr>\n",
       "    <tr>\n",
       "      <th>10</th>\n",
       "      <td>Alcona</td>\n",
       "      <td>Mitchell Twp</td>\n",
       "      <td>Registered Voters</td>\n",
       "      <td>NaN</td>\n",
       "      <td>NaN</td>\n",
       "      <td>NaN</td>\n",
       "      <td>354</td>\n",
       "    </tr>\n",
       "    <tr>\n",
       "      <th>11</th>\n",
       "      <td>Alcona</td>\n",
       "      <td>City Harrisville</td>\n",
       "      <td>Registered Voters</td>\n",
       "      <td>NaN</td>\n",
       "      <td>NaN</td>\n",
       "      <td>NaN</td>\n",
       "      <td>381</td>\n",
       "    </tr>\n",
       "    <tr>\n",
       "      <th>12</th>\n",
       "      <td>Alcona</td>\n",
       "      <td>Alcona Twp</td>\n",
       "      <td>Ballots Cast</td>\n",
       "      <td>NaN</td>\n",
       "      <td>NaN</td>\n",
       "      <td>NaN</td>\n",
       "      <td>276</td>\n",
       "    </tr>\n",
       "    <tr>\n",
       "      <th>13</th>\n",
       "      <td>Alcona</td>\n",
       "      <td>Caledonia Twp</td>\n",
       "      <td>Ballots Cast</td>\n",
       "      <td>NaN</td>\n",
       "      <td>NaN</td>\n",
       "      <td>NaN</td>\n",
       "      <td>242</td>\n",
       "    </tr>\n",
       "    <tr>\n",
       "      <th>14</th>\n",
       "      <td>Alcona</td>\n",
       "      <td>Curtis Twp</td>\n",
       "      <td>Ballots Cast</td>\n",
       "      <td>NaN</td>\n",
       "      <td>NaN</td>\n",
       "      <td>NaN</td>\n",
       "      <td>281</td>\n",
       "    </tr>\n",
       "    <tr>\n",
       "      <th>15</th>\n",
       "      <td>Alcona</td>\n",
       "      <td>Greenbush Twp</td>\n",
       "      <td>Ballots Cast</td>\n",
       "      <td>NaN</td>\n",
       "      <td>NaN</td>\n",
       "      <td>NaN</td>\n",
       "      <td>324</td>\n",
       "    </tr>\n",
       "    <tr>\n",
       "      <th>16</th>\n",
       "      <td>Alcona</td>\n",
       "      <td>Gustin Twp</td>\n",
       "      <td>Ballots Cast</td>\n",
       "      <td>NaN</td>\n",
       "      <td>NaN</td>\n",
       "      <td>NaN</td>\n",
       "      <td>121</td>\n",
       "    </tr>\n",
       "    <tr>\n",
       "      <th>17</th>\n",
       "      <td>Alcona</td>\n",
       "      <td>Harrisville Twp</td>\n",
       "      <td>Ballots Cast</td>\n",
       "      <td>NaN</td>\n",
       "      <td>NaN</td>\n",
       "      <td>NaN</td>\n",
       "      <td>298</td>\n",
       "    </tr>\n",
       "    <tr>\n",
       "      <th>18</th>\n",
       "      <td>Alcona</td>\n",
       "      <td>Hawes Twp</td>\n",
       "      <td>Ballots Cast</td>\n",
       "      <td>NaN</td>\n",
       "      <td>NaN</td>\n",
       "      <td>NaN</td>\n",
       "      <td>186</td>\n",
       "    </tr>\n",
       "    <tr>\n",
       "      <th>19</th>\n",
       "      <td>Alcona</td>\n",
       "      <td>Haynes Twp</td>\n",
       "      <td>Ballots Cast</td>\n",
       "      <td>NaN</td>\n",
       "      <td>NaN</td>\n",
       "      <td>NaN</td>\n",
       "      <td>166</td>\n",
       "    </tr>\n",
       "    <tr>\n",
       "      <th>20</th>\n",
       "      <td>Alcona</td>\n",
       "      <td>Mikado Twp</td>\n",
       "      <td>Ballots Cast</td>\n",
       "      <td>NaN</td>\n",
       "      <td>NaN</td>\n",
       "      <td>NaN</td>\n",
       "      <td>195</td>\n",
       "    </tr>\n",
       "    <tr>\n",
       "      <th>21</th>\n",
       "      <td>Alcona</td>\n",
       "      <td>Millen Twp</td>\n",
       "      <td>Ballots Cast</td>\n",
       "      <td>NaN</td>\n",
       "      <td>NaN</td>\n",
       "      <td>NaN</td>\n",
       "      <td>96</td>\n",
       "    </tr>\n",
       "    <tr>\n",
       "      <th>22</th>\n",
       "      <td>Alcona</td>\n",
       "      <td>Mitchell Twp</td>\n",
       "      <td>Ballots Cast</td>\n",
       "      <td>NaN</td>\n",
       "      <td>NaN</td>\n",
       "      <td>NaN</td>\n",
       "      <td>87</td>\n",
       "    </tr>\n",
       "  </tbody>\n",
       "</table>\n",
       "</div>"
      ],
      "text/plain": [
       "    county          precinct             office  district  party  candidates  \\\n",
       "0   Alcona        Alcona Twp  Registered Voters       NaN    NaN         NaN   \n",
       "1   Alcona     Caledonia Twp  Registered Voters       NaN    NaN         NaN   \n",
       "2   Alcona        Curtis Twp  Registered Voters       NaN    NaN         NaN   \n",
       "3   Alcona     Greenbush Twp  Registered Voters       NaN    NaN         NaN   \n",
       "4   Alcona        Gustin Twp  Registered Voters       NaN    NaN         NaN   \n",
       "5   Alcona   Harrisville Twp  Registered Voters       NaN    NaN         NaN   \n",
       "6   Alcona         Hawes Twp  Registered Voters       NaN    NaN         NaN   \n",
       "7   Alcona        Haynes Twp  Registered Voters       NaN    NaN         NaN   \n",
       "8   Alcona        Mikado Twp  Registered Voters       NaN    NaN         NaN   \n",
       "9   Alcona        Millen Twp  Registered Voters       NaN    NaN         NaN   \n",
       "10  Alcona      Mitchell Twp  Registered Voters       NaN    NaN         NaN   \n",
       "11  Alcona  City Harrisville  Registered Voters       NaN    NaN         NaN   \n",
       "12  Alcona        Alcona Twp       Ballots Cast       NaN    NaN         NaN   \n",
       "13  Alcona     Caledonia Twp       Ballots Cast       NaN    NaN         NaN   \n",
       "14  Alcona        Curtis Twp       Ballots Cast       NaN    NaN         NaN   \n",
       "15  Alcona     Greenbush Twp       Ballots Cast       NaN    NaN         NaN   \n",
       "16  Alcona        Gustin Twp       Ballots Cast       NaN    NaN         NaN   \n",
       "17  Alcona   Harrisville Twp       Ballots Cast       NaN    NaN         NaN   \n",
       "18  Alcona         Hawes Twp       Ballots Cast       NaN    NaN         NaN   \n",
       "19  Alcona        Haynes Twp       Ballots Cast       NaN    NaN         NaN   \n",
       "20  Alcona        Mikado Twp       Ballots Cast       NaN    NaN         NaN   \n",
       "21  Alcona        Millen Twp       Ballots Cast       NaN    NaN         NaN   \n",
       "22  Alcona      Mitchell Twp       Ballots Cast       NaN    NaN         NaN   \n",
       "\n",
       "    votes  \n",
       "0     975  \n",
       "1     955  \n",
       "2    1024  \n",
       "3    1257  \n",
       "4     637  \n",
       "5    1144  \n",
       "6     943  \n",
       "7     645  \n",
       "8     785  \n",
       "9     363  \n",
       "10    354  \n",
       "11    381  \n",
       "12    276  \n",
       "13    242  \n",
       "14    281  \n",
       "15    324  \n",
       "16    121  \n",
       "17    298  \n",
       "18    186  \n",
       "19    166  \n",
       "20    195  \n",
       "21     96  \n",
       "22     87  "
      ]
     },
     "execution_count": 2,
     "metadata": {},
     "output_type": "execute_result"
    }
   ],
   "source": [
    "results_csv = \"\"\"county,precinct,office,district,party,candidates,votes\n",
    "Alcona,Alcona Twp,Registered Voters,,,,975\n",
    "Alcona,Caledonia Twp,Registered Voters,,,,955\n",
    "Alcona,Curtis Twp,Registered Voters,,,,1024\n",
    "Alcona,Greenbush Twp,Registered Voters,,,,1257\n",
    "Alcona,Gustin Twp,Registered Voters,,,,637\n",
    "Alcona,Harrisville Twp,Registered Voters,,,,1144\n",
    "Alcona,Hawes Twp,Registered Voters,,,,943\n",
    "Alcona,Haynes Twp,Registered Voters,,,,645\n",
    "Alcona,Mikado Twp,Registered Voters,,,,785\n",
    "Alcona,Millen Twp,Registered Voters,,,,363\n",
    "Alcona,Mitchell Twp,Registered Voters,,,,354\n",
    "Alcona,City Harrisville,Registered Voters,,,,381\n",
    "Alcona,Alcona Twp,Ballots Cast,,,,276\n",
    "Alcona,Caledonia Twp,Ballots Cast,,,,242\n",
    "Alcona,Curtis Twp,Ballots Cast,,,,281\n",
    "Alcona,Greenbush Twp,Ballots Cast,,,,324\n",
    "Alcona,Gustin Twp,Ballots Cast,,,,121\n",
    "Alcona,Harrisville Twp,Ballots Cast,,,,298\n",
    "Alcona,Hawes Twp,Ballots Cast,,,,186\n",
    "Alcona,Haynes Twp,Ballots Cast,,,,166\n",
    "Alcona,Mikado Twp,Ballots Cast,,,,195\n",
    "Alcona,Millen Twp,Ballots Cast,,,,96\n",
    "Alcona,Mitchell Twp,Ballots Cast,,,,87\n",
    "\"\"\" \n",
    "\n",
    "results = pd.read_csv(io.StringIO(results_csv))\n",
    "\n",
    "results"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "## Create a MultiIndex"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 3,
   "metadata": {},
   "outputs": [
    {
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       "<div>\n",
       "<style scoped>\n",
       "    .dataframe tbody tr th:only-of-type {\n",
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       "\n",
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       "<table border=\"1\" class=\"dataframe\">\n",
       "  <thead>\n",
       "    <tr style=\"text-align: right;\">\n",
       "      <th></th>\n",
       "      <th></th>\n",
       "      <th></th>\n",
       "      <th>district</th>\n",
       "      <th>party</th>\n",
       "      <th>candidates</th>\n",
       "      <th>votes</th>\n",
       "    </tr>\n",
       "    <tr>\n",
       "      <th>county</th>\n",
       "      <th>precinct</th>\n",
       "      <th>office</th>\n",
       "      <th></th>\n",
       "      <th></th>\n",
       "      <th></th>\n",
       "      <th></th>\n",
       "    </tr>\n",
       "  </thead>\n",
       "  <tbody>\n",
       "    <tr>\n",
       "      <th rowspan=\"23\" valign=\"top\">Alcona</th>\n",
       "      <th>Alcona Twp</th>\n",
       "      <th>Registered Voters</th>\n",
       "      <td>NaN</td>\n",
       "      <td>NaN</td>\n",
       "      <td>NaN</td>\n",
       "      <td>975</td>\n",
       "    </tr>\n",
       "    <tr>\n",
       "      <th>Caledonia Twp</th>\n",
       "      <th>Registered Voters</th>\n",
       "      <td>NaN</td>\n",
       "      <td>NaN</td>\n",
       "      <td>NaN</td>\n",
       "      <td>955</td>\n",
       "    </tr>\n",
       "    <tr>\n",
       "      <th>Curtis Twp</th>\n",
       "      <th>Registered Voters</th>\n",
       "      <td>NaN</td>\n",
       "      <td>NaN</td>\n",
       "      <td>NaN</td>\n",
       "      <td>1024</td>\n",
       "    </tr>\n",
       "    <tr>\n",
       "      <th>Greenbush Twp</th>\n",
       "      <th>Registered Voters</th>\n",
       "      <td>NaN</td>\n",
       "      <td>NaN</td>\n",
       "      <td>NaN</td>\n",
       "      <td>1257</td>\n",
       "    </tr>\n",
       "    <tr>\n",
       "      <th>Gustin Twp</th>\n",
       "      <th>Registered Voters</th>\n",
       "      <td>NaN</td>\n",
       "      <td>NaN</td>\n",
       "      <td>NaN</td>\n",
       "      <td>637</td>\n",
       "    </tr>\n",
       "    <tr>\n",
       "      <th>Harrisville Twp</th>\n",
       "      <th>Registered Voters</th>\n",
       "      <td>NaN</td>\n",
       "      <td>NaN</td>\n",
       "      <td>NaN</td>\n",
       "      <td>1144</td>\n",
       "    </tr>\n",
       "    <tr>\n",
       "      <th>Hawes Twp</th>\n",
       "      <th>Registered Voters</th>\n",
       "      <td>NaN</td>\n",
       "      <td>NaN</td>\n",
       "      <td>NaN</td>\n",
       "      <td>943</td>\n",
       "    </tr>\n",
       "    <tr>\n",
       "      <th>Haynes Twp</th>\n",
       "      <th>Registered Voters</th>\n",
       "      <td>NaN</td>\n",
       "      <td>NaN</td>\n",
       "      <td>NaN</td>\n",
       "      <td>645</td>\n",
       "    </tr>\n",
       "    <tr>\n",
       "      <th>Mikado Twp</th>\n",
       "      <th>Registered Voters</th>\n",
       "      <td>NaN</td>\n",
       "      <td>NaN</td>\n",
       "      <td>NaN</td>\n",
       "      <td>785</td>\n",
       "    </tr>\n",
       "    <tr>\n",
       "      <th>Millen Twp</th>\n",
       "      <th>Registered Voters</th>\n",
       "      <td>NaN</td>\n",
       "      <td>NaN</td>\n",
       "      <td>NaN</td>\n",
       "      <td>363</td>\n",
       "    </tr>\n",
       "    <tr>\n",
       "      <th>Mitchell Twp</th>\n",
       "      <th>Registered Voters</th>\n",
       "      <td>NaN</td>\n",
       "      <td>NaN</td>\n",
       "      <td>NaN</td>\n",
       "      <td>354</td>\n",
       "    </tr>\n",
       "    <tr>\n",
       "      <th>City Harrisville</th>\n",
       "      <th>Registered Voters</th>\n",
       "      <td>NaN</td>\n",
       "      <td>NaN</td>\n",
       "      <td>NaN</td>\n",
       "      <td>381</td>\n",
       "    </tr>\n",
       "    <tr>\n",
       "      <th>Alcona Twp</th>\n",
       "      <th>Ballots Cast</th>\n",
       "      <td>NaN</td>\n",
       "      <td>NaN</td>\n",
       "      <td>NaN</td>\n",
       "      <td>276</td>\n",
       "    </tr>\n",
       "    <tr>\n",
       "      <th>Caledonia Twp</th>\n",
       "      <th>Ballots Cast</th>\n",
       "      <td>NaN</td>\n",
       "      <td>NaN</td>\n",
       "      <td>NaN</td>\n",
       "      <td>242</td>\n",
       "    </tr>\n",
       "    <tr>\n",
       "      <th>Curtis Twp</th>\n",
       "      <th>Ballots Cast</th>\n",
       "      <td>NaN</td>\n",
       "      <td>NaN</td>\n",
       "      <td>NaN</td>\n",
       "      <td>281</td>\n",
       "    </tr>\n",
       "    <tr>\n",
       "      <th>Greenbush Twp</th>\n",
       "      <th>Ballots Cast</th>\n",
       "      <td>NaN</td>\n",
       "      <td>NaN</td>\n",
       "      <td>NaN</td>\n",
       "      <td>324</td>\n",
       "    </tr>\n",
       "    <tr>\n",
       "      <th>Gustin Twp</th>\n",
       "      <th>Ballots Cast</th>\n",
       "      <td>NaN</td>\n",
       "      <td>NaN</td>\n",
       "      <td>NaN</td>\n",
       "      <td>121</td>\n",
       "    </tr>\n",
       "    <tr>\n",
       "      <th>Harrisville Twp</th>\n",
       "      <th>Ballots Cast</th>\n",
       "      <td>NaN</td>\n",
       "      <td>NaN</td>\n",
       "      <td>NaN</td>\n",
       "      <td>298</td>\n",
       "    </tr>\n",
       "    <tr>\n",
       "      <th>Hawes Twp</th>\n",
       "      <th>Ballots Cast</th>\n",
       "      <td>NaN</td>\n",
       "      <td>NaN</td>\n",
       "      <td>NaN</td>\n",
       "      <td>186</td>\n",
       "    </tr>\n",
       "    <tr>\n",
       "      <th>Haynes Twp</th>\n",
       "      <th>Ballots Cast</th>\n",
       "      <td>NaN</td>\n",
       "      <td>NaN</td>\n",
       "      <td>NaN</td>\n",
       "      <td>166</td>\n",
       "    </tr>\n",
       "    <tr>\n",
       "      <th>Mikado Twp</th>\n",
       "      <th>Ballots Cast</th>\n",
       "      <td>NaN</td>\n",
       "      <td>NaN</td>\n",
       "      <td>NaN</td>\n",
       "      <td>195</td>\n",
       "    </tr>\n",
       "    <tr>\n",
       "      <th>Millen Twp</th>\n",
       "      <th>Ballots Cast</th>\n",
       "      <td>NaN</td>\n",
       "      <td>NaN</td>\n",
       "      <td>NaN</td>\n",
       "      <td>96</td>\n",
       "    </tr>\n",
       "    <tr>\n",
       "      <th>Mitchell Twp</th>\n",
       "      <th>Ballots Cast</th>\n",
       "      <td>NaN</td>\n",
       "      <td>NaN</td>\n",
       "      <td>NaN</td>\n",
       "      <td>87</td>\n",
       "    </tr>\n",
       "  </tbody>\n",
       "</table>\n",
       "</div>"
      ],
      "text/plain": [
       "                                           district  party  candidates  votes\n",
       "county precinct         office                                               \n",
       "Alcona Alcona Twp       Registered Voters       NaN    NaN         NaN    975\n",
       "       Caledonia Twp    Registered Voters       NaN    NaN         NaN    955\n",
       "       Curtis Twp       Registered Voters       NaN    NaN         NaN   1024\n",
       "       Greenbush Twp    Registered Voters       NaN    NaN         NaN   1257\n",
       "       Gustin Twp       Registered Voters       NaN    NaN         NaN    637\n",
       "       Harrisville Twp  Registered Voters       NaN    NaN         NaN   1144\n",
       "       Hawes Twp        Registered Voters       NaN    NaN         NaN    943\n",
       "       Haynes Twp       Registered Voters       NaN    NaN         NaN    645\n",
       "       Mikado Twp       Registered Voters       NaN    NaN         NaN    785\n",
       "       Millen Twp       Registered Voters       NaN    NaN         NaN    363\n",
       "       Mitchell Twp     Registered Voters       NaN    NaN         NaN    354\n",
       "       City Harrisville Registered Voters       NaN    NaN         NaN    381\n",
       "       Alcona Twp       Ballots Cast            NaN    NaN         NaN    276\n",
       "       Caledonia Twp    Ballots Cast            NaN    NaN         NaN    242\n",
       "       Curtis Twp       Ballots Cast            NaN    NaN         NaN    281\n",
       "       Greenbush Twp    Ballots Cast            NaN    NaN         NaN    324\n",
       "       Gustin Twp       Ballots Cast            NaN    NaN         NaN    121\n",
       "       Harrisville Twp  Ballots Cast            NaN    NaN         NaN    298\n",
       "       Hawes Twp        Ballots Cast            NaN    NaN         NaN    186\n",
       "       Haynes Twp       Ballots Cast            NaN    NaN         NaN    166\n",
       "       Mikado Twp       Ballots Cast            NaN    NaN         NaN    195\n",
       "       Millen Twp       Ballots Cast            NaN    NaN         NaN     96\n",
       "       Mitchell Twp     Ballots Cast            NaN    NaN         NaN     87"
      ]
     },
     "execution_count": 3,
     "metadata": {},
     "output_type": "execute_result"
    }
   ],
   "source": [
    "results = results.set_index([\"county\", \"precinct\", \"office\"])\n",
    "\n",
    "results"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "## Use `slice(None)` to select any value at a particular level of the MultiIndex\n",
    "\n",
    "Let's say we want to get values for \"Ballots Cast\", for any county or precinct. We can use `.loc` and specify `slice(None)` for the levels of the index for which we want to get any value.\n",
    "\n",
    "Before we do this, it might be useful to recall how to get a single value using `.loc` and a MultiIndex."
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 4,
   "metadata": {},
   "outputs": [
    {
     "data": {
      "text/plain": [
       "district        NaN\n",
       "party           NaN\n",
       "candidates      NaN\n",
       "votes         242.0\n",
       "Name: (Alcona, Caledonia Twp, Ballots Cast), dtype: float64"
      ]
     },
     "execution_count": 4,
     "metadata": {},
     "output_type": "execute_result"
    }
   ],
   "source": [
    "results.loc[(\"Alcona\", \"Caledonia Twp\", \"Ballots Cast\")]"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "To get all values for the \"Ballots Cast\" \"office\", we'll specify `slice(None)` for the `county` and `precinct` levels."
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 5,
   "metadata": {},
   "outputs": [
    {
     "data": {
      "text/html": [
       "<div>\n",
       "<style scoped>\n",
       "    .dataframe tbody tr th:only-of-type {\n",
       "        vertical-align: middle;\n",
       "    }\n",
       "\n",
       "    .dataframe tbody tr th {\n",
       "        vertical-align: top;\n",
       "    }\n",
       "\n",
       "    .dataframe thead th {\n",
       "        text-align: right;\n",
       "    }\n",
       "</style>\n",
       "<table border=\"1\" class=\"dataframe\">\n",
       "  <thead>\n",
       "    <tr style=\"text-align: right;\">\n",
       "      <th></th>\n",
       "      <th></th>\n",
       "      <th></th>\n",
       "      <th>district</th>\n",
       "      <th>party</th>\n",
       "      <th>candidates</th>\n",
       "      <th>votes</th>\n",
       "    </tr>\n",
       "    <tr>\n",
       "      <th>county</th>\n",
       "      <th>precinct</th>\n",
       "      <th>office</th>\n",
       "      <th></th>\n",
       "      <th></th>\n",
       "      <th></th>\n",
       "      <th></th>\n",
       "    </tr>\n",
       "  </thead>\n",
       "  <tbody>\n",
       "    <tr>\n",
       "      <th rowspan=\"11\" valign=\"top\">Alcona</th>\n",
       "      <th>Alcona Twp</th>\n",
       "      <th>Ballots Cast</th>\n",
       "      <td>NaN</td>\n",
       "      <td>NaN</td>\n",
       "      <td>NaN</td>\n",
       "      <td>276</td>\n",
       "    </tr>\n",
       "    <tr>\n",
       "      <th>Caledonia Twp</th>\n",
       "      <th>Ballots Cast</th>\n",
       "      <td>NaN</td>\n",
       "      <td>NaN</td>\n",
       "      <td>NaN</td>\n",
       "      <td>242</td>\n",
       "    </tr>\n",
       "    <tr>\n",
       "      <th>Curtis Twp</th>\n",
       "      <th>Ballots Cast</th>\n",
       "      <td>NaN</td>\n",
       "      <td>NaN</td>\n",
       "      <td>NaN</td>\n",
       "      <td>281</td>\n",
       "    </tr>\n",
       "    <tr>\n",
       "      <th>Greenbush Twp</th>\n",
       "      <th>Ballots Cast</th>\n",
       "      <td>NaN</td>\n",
       "      <td>NaN</td>\n",
       "      <td>NaN</td>\n",
       "      <td>324</td>\n",
       "    </tr>\n",
       "    <tr>\n",
       "      <th>Gustin Twp</th>\n",
       "      <th>Ballots Cast</th>\n",
       "      <td>NaN</td>\n",
       "      <td>NaN</td>\n",
       "      <td>NaN</td>\n",
       "      <td>121</td>\n",
       "    </tr>\n",
       "    <tr>\n",
       "      <th>Harrisville Twp</th>\n",
       "      <th>Ballots Cast</th>\n",
       "      <td>NaN</td>\n",
       "      <td>NaN</td>\n",
       "      <td>NaN</td>\n",
       "      <td>298</td>\n",
       "    </tr>\n",
       "    <tr>\n",
       "      <th>Hawes Twp</th>\n",
       "      <th>Ballots Cast</th>\n",
       "      <td>NaN</td>\n",
       "      <td>NaN</td>\n",
       "      <td>NaN</td>\n",
       "      <td>186</td>\n",
       "    </tr>\n",
       "    <tr>\n",
       "      <th>Haynes Twp</th>\n",
       "      <th>Ballots Cast</th>\n",
       "      <td>NaN</td>\n",
       "      <td>NaN</td>\n",
       "      <td>NaN</td>\n",
       "      <td>166</td>\n",
       "    </tr>\n",
       "    <tr>\n",
       "      <th>Mikado Twp</th>\n",
       "      <th>Ballots Cast</th>\n",
       "      <td>NaN</td>\n",
       "      <td>NaN</td>\n",
       "      <td>NaN</td>\n",
       "      <td>195</td>\n",
       "    </tr>\n",
       "    <tr>\n",
       "      <th>Millen Twp</th>\n",
       "      <th>Ballots Cast</th>\n",
       "      <td>NaN</td>\n",
       "      <td>NaN</td>\n",
       "      <td>NaN</td>\n",
       "      <td>96</td>\n",
       "    </tr>\n",
       "    <tr>\n",
       "      <th>Mitchell Twp</th>\n",
       "      <th>Ballots Cast</th>\n",
       "      <td>NaN</td>\n",
       "      <td>NaN</td>\n",
       "      <td>NaN</td>\n",
       "      <td>87</td>\n",
       "    </tr>\n",
       "  </tbody>\n",
       "</table>\n",
       "</div>"
      ],
      "text/plain": [
       "                                     district  party  candidates  votes\n",
       "county precinct        office                                          \n",
       "Alcona Alcona Twp      Ballots Cast       NaN    NaN         NaN    276\n",
       "       Caledonia Twp   Ballots Cast       NaN    NaN         NaN    242\n",
       "       Curtis Twp      Ballots Cast       NaN    NaN         NaN    281\n",
       "       Greenbush Twp   Ballots Cast       NaN    NaN         NaN    324\n",
       "       Gustin Twp      Ballots Cast       NaN    NaN         NaN    121\n",
       "       Harrisville Twp Ballots Cast       NaN    NaN         NaN    298\n",
       "       Hawes Twp       Ballots Cast       NaN    NaN         NaN    186\n",
       "       Haynes Twp      Ballots Cast       NaN    NaN         NaN    166\n",
       "       Mikado Twp      Ballots Cast       NaN    NaN         NaN    195\n",
       "       Millen Twp      Ballots Cast       NaN    NaN         NaN     96\n",
       "       Mitchell Twp    Ballots Cast       NaN    NaN         NaN     87"
      ]
     },
     "execution_count": 5,
     "metadata": {},
     "output_type": "execute_result"
    }
   ],
   "source": [
    "results.loc[(slice(None), slice(None), \"Ballots Cast\"), :]"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "## Or, use `pandas.IndexSlice`\n",
    "\n",
    "Instead of using `slice(None)` we can use [pandas.IndexSlice ](https://pandas.pydata.org/pandas-docs/stable/reference/api/pandas.IndexSlice.html#pandas.IndexSlice) to use a syntax similar to how you would slice an array."
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 6,
   "metadata": {},
   "outputs": [
    {
     "data": {
      "text/html": [
       "<div>\n",
       "<style scoped>\n",
       "    .dataframe tbody tr th:only-of-type {\n",
       "        vertical-align: middle;\n",
       "    }\n",
       "\n",
       "    .dataframe tbody tr th {\n",
       "        vertical-align: top;\n",
       "    }\n",
       "\n",
       "    .dataframe thead th {\n",
       "        text-align: right;\n",
       "    }\n",
       "</style>\n",
       "<table border=\"1\" class=\"dataframe\">\n",
       "  <thead>\n",
       "    <tr style=\"text-align: right;\">\n",
       "      <th></th>\n",
       "      <th></th>\n",
       "      <th></th>\n",
       "      <th>district</th>\n",
       "      <th>party</th>\n",
       "      <th>candidates</th>\n",
       "      <th>votes</th>\n",
       "    </tr>\n",
       "    <tr>\n",
       "      <th>county</th>\n",
       "      <th>precinct</th>\n",
       "      <th>office</th>\n",
       "      <th></th>\n",
       "      <th></th>\n",
       "      <th></th>\n",
       "      <th></th>\n",
       "    </tr>\n",
       "  </thead>\n",
       "  <tbody>\n",
       "    <tr>\n",
       "      <th rowspan=\"11\" valign=\"top\">Alcona</th>\n",
       "      <th>Alcona Twp</th>\n",
       "      <th>Ballots Cast</th>\n",
       "      <td>NaN</td>\n",
       "      <td>NaN</td>\n",
       "      <td>NaN</td>\n",
       "      <td>276</td>\n",
       "    </tr>\n",
       "    <tr>\n",
       "      <th>Caledonia Twp</th>\n",
       "      <th>Ballots Cast</th>\n",
       "      <td>NaN</td>\n",
       "      <td>NaN</td>\n",
       "      <td>NaN</td>\n",
       "      <td>242</td>\n",
       "    </tr>\n",
       "    <tr>\n",
       "      <th>Curtis Twp</th>\n",
       "      <th>Ballots Cast</th>\n",
       "      <td>NaN</td>\n",
       "      <td>NaN</td>\n",
       "      <td>NaN</td>\n",
       "      <td>281</td>\n",
       "    </tr>\n",
       "    <tr>\n",
       "      <th>Greenbush Twp</th>\n",
       "      <th>Ballots Cast</th>\n",
       "      <td>NaN</td>\n",
       "      <td>NaN</td>\n",
       "      <td>NaN</td>\n",
       "      <td>324</td>\n",
       "    </tr>\n",
       "    <tr>\n",
       "      <th>Gustin Twp</th>\n",
       "      <th>Ballots Cast</th>\n",
       "      <td>NaN</td>\n",
       "      <td>NaN</td>\n",
       "      <td>NaN</td>\n",
       "      <td>121</td>\n",
       "    </tr>\n",
       "    <tr>\n",
       "      <th>Harrisville Twp</th>\n",
       "      <th>Ballots Cast</th>\n",
       "      <td>NaN</td>\n",
       "      <td>NaN</td>\n",
       "      <td>NaN</td>\n",
       "      <td>298</td>\n",
       "    </tr>\n",
       "    <tr>\n",
       "      <th>Hawes Twp</th>\n",
       "      <th>Ballots Cast</th>\n",
       "      <td>NaN</td>\n",
       "      <td>NaN</td>\n",
       "      <td>NaN</td>\n",
       "      <td>186</td>\n",
       "    </tr>\n",
       "    <tr>\n",
       "      <th>Haynes Twp</th>\n",
       "      <th>Ballots Cast</th>\n",
       "      <td>NaN</td>\n",
       "      <td>NaN</td>\n",
       "      <td>NaN</td>\n",
       "      <td>166</td>\n",
       "    </tr>\n",
       "    <tr>\n",
       "      <th>Mikado Twp</th>\n",
       "      <th>Ballots Cast</th>\n",
       "      <td>NaN</td>\n",
       "      <td>NaN</td>\n",
       "      <td>NaN</td>\n",
       "      <td>195</td>\n",
       "    </tr>\n",
       "    <tr>\n",
       "      <th>Millen Twp</th>\n",
       "      <th>Ballots Cast</th>\n",
       "      <td>NaN</td>\n",
       "      <td>NaN</td>\n",
       "      <td>NaN</td>\n",
       "      <td>96</td>\n",
       "    </tr>\n",
       "    <tr>\n",
       "      <th>Mitchell Twp</th>\n",
       "      <th>Ballots Cast</th>\n",
       "      <td>NaN</td>\n",
       "      <td>NaN</td>\n",
       "      <td>NaN</td>\n",
       "      <td>87</td>\n",
       "    </tr>\n",
       "  </tbody>\n",
       "</table>\n",
       "</div>"
      ],
      "text/plain": [
       "                                     district  party  candidates  votes\n",
       "county precinct        office                                          \n",
       "Alcona Alcona Twp      Ballots Cast       NaN    NaN         NaN    276\n",
       "       Caledonia Twp   Ballots Cast       NaN    NaN         NaN    242\n",
       "       Curtis Twp      Ballots Cast       NaN    NaN         NaN    281\n",
       "       Greenbush Twp   Ballots Cast       NaN    NaN         NaN    324\n",
       "       Gustin Twp      Ballots Cast       NaN    NaN         NaN    121\n",
       "       Harrisville Twp Ballots Cast       NaN    NaN         NaN    298\n",
       "       Hawes Twp       Ballots Cast       NaN    NaN         NaN    186\n",
       "       Haynes Twp      Ballots Cast       NaN    NaN         NaN    166\n",
       "       Mikado Twp      Ballots Cast       NaN    NaN         NaN    195\n",
       "       Millen Twp      Ballots Cast       NaN    NaN         NaN     96\n",
       "       Mitchell Twp    Ballots Cast       NaN    NaN         NaN     87"
      ]
     },
     "execution_count": 6,
     "metadata": {},
     "output_type": "execute_result"
    }
   ],
   "source": [
    "idx = pd.IndexSlice\n",
    "\n",
    "results.loc[idx[:, :, \"Ballots Cast\"], :]"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": null,
   "metadata": {},
   "outputs": [],
   "source": []
  }
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