Find-elements-index-value-in-pandas-series.ipynb

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  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "# Finding the index of an element in a Pandas Series\n",
    "\n",
    "These examples are based on the responses to a Stackoverflow question:\n",
    "- [Find element's index in pandas Series](https://stackoverflow.com/questions/18327624/find-elements-index-in-pandas-series/57741928?noredirect=1#comment109291001_57741928)"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 1,
   "metadata": {},
   "outputs": [],
   "source": [
    "from platform import python_version\n",
    "python_version()"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 2,
   "metadata": {},
   "outputs": [
    {
     "data": {
      "text/plain": [
       "('1.18.1', '1.0.2')"
      ]
     },
     "execution_count": 2,
     "metadata": {},
     "output_type": "execute_result"
    }
   ],
   "source": [
    "import numpy as np\n",
    "import pandas as pd\n",
    "\n",
    "np.__version__, pd.__version__"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 3,
   "metadata": {},
   "outputs": [],
   "source": [
    "data = [406400, 203200, 101600,  76100,  50800,  25400,  19050,  12700, \n",
    "         9500,   6700,   4750,   3350,   2360,   1700,   1180,    850, \n",
    "          600,    425,    300,    212,    150,    106,     75,     53, \n",
    "           38]\n",
    "myseries = pd.Series(data, index=range(1,26))"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 4,
   "metadata": {},
   "outputs": [
    {
     "data": {
      "text/plain": [
       "150"
      ]
     },
     "execution_count": 4,
     "metadata": {},
     "output_type": "execute_result"
    }
   ],
   "source": [
    "myseries[21]"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 5,
   "metadata": {},
   "outputs": [
    {
     "name": "stdout",
     "output_type": "stream",
     "text": [
      "427 µs ± 6.76 µs per loop (mean ± std. dev. of 7 runs, 1000 loops each)\n"
     ]
    }
   ],
   "source": [
    "assert myseries[myseries == 150].index[0] == 21\n",
    "%timeit myseries[myseries == 150].index[0]"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 6,
   "metadata": {},
   "outputs": [
    {
     "name": "stdout",
     "output_type": "stream",
     "text": [
      "466 µs ± 3.61 µs per loop (mean ± std. dev. of 7 runs, 1000 loops each)\n"
     ]
    }
   ],
   "source": [
    "assert myseries[myseries == 150].first_valid_index() == 21\n",
    "%timeit myseries[myseries == 150].first_valid_index()"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 7,
   "metadata": {},
   "outputs": [
    {
     "name": "stdout",
     "output_type": "stream",
     "text": [
      "571 µs ± 11.8 µs per loop (mean ± std. dev. of 7 runs, 1000 loops each)\n"
     ]
    }
   ],
   "source": [
    "assert myseries.where(myseries == 150).first_valid_index() == 21\n",
    "%timeit myseries.where(myseries == 150).first_valid_index()"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 8,
   "metadata": {},
   "outputs": [
    {
     "name": "stdout",
     "output_type": "stream",
     "text": [
      "137 µs ± 3.22 µs per loop (mean ± std. dev. of 7 runs, 10000 loops each)\n"
     ]
    }
   ],
   "source": [
    "assert myseries.index[np.where(myseries == 150)[0][0]] == 21\n",
    "%timeit myseries.index[np.where(myseries == 150)[0][0]]"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 9,
   "metadata": {},
   "outputs": [
    {
     "name": "stdout",
     "output_type": "stream",
     "text": [
      "214 µs ± 5.58 µs per loop (mean ± std. dev. of 7 runs, 1000 loops each)\n"
     ]
    }
   ],
   "source": [
    "assert pd.Series(myseries.index, index=myseries)[150] == 21\n",
    "%timeit pd.Series(myseries.index, index=myseries)[150]"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 10,
   "metadata": {},
   "outputs": [
    {
     "name": "stdout",
     "output_type": "stream",
     "text": [
      "93.6 µs ± 502 ns per loop (mean ± std. dev. of 7 runs, 10000 loops each)\n"
     ]
    }
   ],
   "source": [
    "assert myseries.index[pd.Index(myseries).get_loc(150)] == 21\n",
    "%timeit myseries.index[pd.Index(myseries).get_loc(150)]"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 11,
   "metadata": {},
   "outputs": [
    {
     "name": "stdout",
     "output_type": "stream",
     "text": [
      "11.1 µs ± 36.1 ns per loop (mean ± std. dev. of 7 runs, 100000 loops each)\n"
     ]
    }
   ],
   "source": [
    "assert myseries.index[list(myseries).index(150)] == 21\n",
    "%timeit myseries.index[list(myseries).index(150)]"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 12,
   "metadata": {},
   "outputs": [
    {
     "name": "stdout",
     "output_type": "stream",
     "text": [
      "6.46 µs ± 72.8 ns per loop (mean ± std. dev. of 7 runs, 100000 loops each)\n"
     ]
    }
   ],
   "source": [
    "assert myseries.index[myseries.tolist().index(150)] == 21\n",
    "%timeit myseries.index[myseries.tolist().index(150)]"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 13,
   "metadata": {},
   "outputs": [
    {
     "name": "stdout",
     "output_type": "stream",
     "text": [
      "5.82 µs ± 88.2 ns per loop (mean ± std. dev. of 7 runs, 100000 loops each)\n"
     ]
    }
   ],
   "source": [
    "assert myseries.index[(myseries.values == 150).argmax()] == 21\n",
    "%timeit myseries.index[(myseries.values == 150).argmax()]"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 14,
   "metadata": {},
   "outputs": [
    {
     "name": "stdout",
     "output_type": "stream",
     "text": [
      "2.39 µs ± 28.7 ns per loop (mean ± std. dev. of 7 runs, 100000 loops each)\n"
     ]
    }
   ],
   "source": [
    "# If you are sure myseries will not change, you can do additional lookups \n",
    "# very quickly using the .get_loc() method\n",
    "lookup_index = pd.Index(myseries)\n",
    "assert myseries.index[lookup_index.get_loc(150)] == 21\n",
    "%timeit myseries.index[lookup_index.get_loc(150)]"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": null,
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   "execution_count": null,
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   "source": []
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   "cell_type": "code",
   "execution_count": null,
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   "source": []
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  {
   "cell_type": "code",
   "execution_count": null,
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