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    "# Pre-Tutorial Exercises\n",
    "\n",
    "If you've arrived early for the tutorial, please feel free to attempt the following exercises to warm-up."
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    "# 1. Basic Python data structures\n",
    "# I have a list of dictionaries as such:\n",
    "\n",
    "names = [{'name': 'Eric',\n",
    "          'surname': 'Ma'},\n",
    "         {'name': 'Jeffrey',\n",
    "          'surname': 'Elmer'},\n",
    "         {'name': 'Mike',\n",
    "          'surname': 'Lee'},\n",
    "         {'name': 'Jennifer',\n",
    "          'surname': 'Elmer'}]\n",
    "\n",
    "# Write a function that takes in a list of dictionaries and a query surname, \n",
    "# and searches it for all individuals with a given surname.\n",
    "\n",
    "def find_persons_with_surname(persons, query_surname):\n",
    "    # Assert that the persons parameter is a list. \n",
    "    # This is a good defensive programming practice.\n",
    "    assert isinstance(persons, list)   \n",
    "    \n",
    "    results = []\n",
    "    for ______ in ______:\n",
    "        if ___________ == __________:\n",
    "            results.append(________)\n",
    "    \n",
    "    return results"
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     "ename": "UnboundLocalError",
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     "output_type": "error",
     "traceback": [
      "\u001b[0;31m---------------------------------------------------------------------------\u001b[0m",
      "\u001b[0;31mUnboundLocalError\u001b[0m                         Traceback (most recent call last)",
      "\u001b[0;32m<ipython-input-2-d7bd54c0478d>\u001b[0m in \u001b[0;36m<module>\u001b[0;34m()\u001b[0m\n\u001b[1;32m      1\u001b[0m \u001b[0;31m# Test your result below.\u001b[0m\u001b[0;34m\u001b[0m\u001b[0;34m\u001b[0m\u001b[0m\n\u001b[0;32m----> 2\u001b[0;31m \u001b[0mresults\u001b[0m \u001b[0;34m=\u001b[0m \u001b[0mfind_persons_with_surname\u001b[0m\u001b[0;34m(\u001b[0m\u001b[0mnames\u001b[0m\u001b[0;34m,\u001b[0m \u001b[0;34m'Lee'\u001b[0m\u001b[0;34m)\u001b[0m\u001b[0;34m\u001b[0m\u001b[0m\n\u001b[0m\u001b[1;32m      3\u001b[0m \u001b[0;32massert\u001b[0m \u001b[0mlen\u001b[0m\u001b[0;34m(\u001b[0m\u001b[0mresults\u001b[0m\u001b[0;34m)\u001b[0m \u001b[0;34m==\u001b[0m \u001b[0;36m1\u001b[0m\u001b[0;34m\u001b[0m\u001b[0m\n\u001b[1;32m      4\u001b[0m \u001b[0;34m\u001b[0m\u001b[0m\n\u001b[1;32m      5\u001b[0m \u001b[0mresults\u001b[0m \u001b[0;34m=\u001b[0m \u001b[0mfind_persons_with_surname\u001b[0m\u001b[0;34m(\u001b[0m\u001b[0mnames\u001b[0m\u001b[0;34m,\u001b[0m \u001b[0;34m'Elmer'\u001b[0m\u001b[0;34m)\u001b[0m\u001b[0;34m\u001b[0m\u001b[0m\n",
      "\u001b[0;32m<ipython-input-1-5332cbff266c>\u001b[0m in \u001b[0;36mfind_persons_with_surname\u001b[0;34m(persons, query_surname)\u001b[0m\n\u001b[1;32m     20\u001b[0m \u001b[0;34m\u001b[0m\u001b[0m\n\u001b[1;32m     21\u001b[0m     \u001b[0mresults\u001b[0m \u001b[0;34m=\u001b[0m \u001b[0;34m[\u001b[0m\u001b[0;34m]\u001b[0m\u001b[0;34m\u001b[0m\u001b[0m\n\u001b[0;32m---> 22\u001b[0;31m     \u001b[0;32mfor\u001b[0m \u001b[0m______\u001b[0m \u001b[0;32min\u001b[0m \u001b[0m______\u001b[0m\u001b[0;34m:\u001b[0m\u001b[0;34m\u001b[0m\u001b[0m\n\u001b[0m\u001b[1;32m     23\u001b[0m         \u001b[0;32mif\u001b[0m \u001b[0m___________\u001b[0m \u001b[0;34m==\u001b[0m \u001b[0m__________\u001b[0m\u001b[0;34m:\u001b[0m\u001b[0;34m\u001b[0m\u001b[0m\n\u001b[1;32m     24\u001b[0m             \u001b[0mresults\u001b[0m\u001b[0;34m.\u001b[0m\u001b[0mappend\u001b[0m\u001b[0;34m(\u001b[0m\u001b[0m________\u001b[0m\u001b[0;34m)\u001b[0m\u001b[0;34m\u001b[0m\u001b[0m\n",
      "\u001b[0;31mUnboundLocalError\u001b[0m: local variable '______' referenced before assignment"
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    "# Test your result below.\n",
    "results = find_persons_with_surname(names, 'Lee')\n",
    "assert len(results) == 1\n",
    "\n",
    "results = find_persons_with_surname(names, 'Elmer')\n",
    "assert len(results) == 2"
   ]
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