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   "source": [
    "# enumerate()\n",
    "\n",
    "In this lecture we will learn about an extremely useful built-in function: enumerate(). Enumerate allows you to keep a count as you iterate through an object. It does this by returning a tuple in the form (count,element). The function itself is equivalent to:\n",
    "\n",
    "    def enumerate(sequence, start=0):\n",
    "        n = start\n",
    "        for elem in sequence:\n",
    "            yield n, elem\n",
    "            n += 1\n",
    "\n",
    "## Example"
   ]
  },
  {
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   "outputs": [
    {
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     "text": [
      "0\n",
      "a\n",
      "1\n",
      "b\n",
      "2\n",
      "c\n"
     ]
    }
   ],
   "source": [
    "lst = ['a','b','c']\n",
    "\n",
    "for number,item in enumerate(lst):\n",
    "    print(number)\n",
    "    print(item)"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "enumerate() becomes particularly useful when you have a case where you need to have some sort of tracker. For example:"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 2,
   "metadata": {},
   "outputs": [
    {
     "name": "stdout",
     "output_type": "stream",
     "text": [
      "a\n",
      "b\n"
     ]
    }
   ],
   "source": [
    "for count,item in enumerate(lst):\n",
    "    if count >= 2:\n",
    "        break\n",
    "    else:\n",
    "        print(item)"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "enumerate() takes an optional \"start\" argument to override the default value of zero:"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 3,
   "metadata": {},
   "outputs": [
    {
     "data": {
      "text/plain": [
       "[(3, 'March'), (4, 'April'), (5, 'May'), (6, 'June')]"
      ]
     },
     "execution_count": 3,
     "metadata": {},
     "output_type": "execute_result"
    }
   ],
   "source": [
    "months = ['March','April','May','June']\n",
    "\n",
    "list(enumerate(months,start=3))"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "Great! You should now have a good understanding of enumerate and its potential use cases."
   ]
  }
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