Iterate over the rows of a dataframe, and expand some rows into multiple rows.

expand_rows.ipynb

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   "execution_count": 55,
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   "source": [
    "import pandas as pd\n",
    "import toolz as tz"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 59,
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     "data": {
      "text/html": [
       "<div>\n",
       "<table border=\"1\" class=\"dataframe\">\n",
       "  <thead>\n",
       "    <tr style=\"text-align: right;\">\n",
       "      <th></th>\n",
       "      <th>a</th>\n",
       "      <th>b</th>\n",
       "    </tr>\n",
       "  </thead>\n",
       "  <tbody>\n",
       "    <tr>\n",
       "      <th>0</th>\n",
       "      <td>1</td>\n",
       "      <td>10</td>\n",
       "    </tr>\n",
       "    <tr>\n",
       "      <th>1</th>\n",
       "      <td>2</td>\n",
       "      <td>20</td>\n",
       "    </tr>\n",
       "    <tr>\n",
       "      <th>2</th>\n",
       "      <td>3,4</td>\n",
       "      <td>30</td>\n",
       "    </tr>\n",
       "  </tbody>\n",
       "</table>\n",
       "</div>"
      ],
      "text/plain": [
       "     a   b\n",
       "0    1  10\n",
       "1    2  20\n",
       "2  3,4  30"
      ]
     },
     "execution_count": 59,
     "metadata": {},
     "output_type": "execute_result"
    }
   ],
   "source": [
    "df = pd.DataFrame({\"a\":['1','2','3,4'], \"b\": [10,20,30]})\n",
    "df"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 61,
   "metadata": {
    "collapsed": false
   },
   "outputs": [
    {
     "name": "stdout",
     "output_type": "stream",
     "text": [
      "{'a': '1', 'b': 10}\n",
      "{'a': '2', 'b': 20}\n",
      "{'a': '3,4', 'b': 30}\n"
     ]
    }
   ],
   "source": [
    "rows = [y for x,y in list(df.T.to_dict().iteritems())] # break the dataframe into rows represented as dictionaries. \n",
    "for row in rows:\n",
    "    print row"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 62,
   "metadata": {
    "collapsed": false
   },
   "outputs": [
    {
     "data": {
      "text/html": [
       "<div>\n",
       "<table border=\"1\" class=\"dataframe\">\n",
       "  <thead>\n",
       "    <tr style=\"text-align: right;\">\n",
       "      <th></th>\n",
       "      <th>a</th>\n",
       "      <th>b</th>\n",
       "    </tr>\n",
       "  </thead>\n",
       "  <tbody>\n",
       "    <tr>\n",
       "      <th>0</th>\n",
       "      <td>1</td>\n",
       "      <td>10</td>\n",
       "    </tr>\n",
       "    <tr>\n",
       "      <th>1</th>\n",
       "      <td>2</td>\n",
       "      <td>20</td>\n",
       "    </tr>\n",
       "    <tr>\n",
       "      <th>2</th>\n",
       "      <td>3</td>\n",
       "      <td>30</td>\n",
       "    </tr>\n",
       "    <tr>\n",
       "      <th>3</th>\n",
       "      <td>4</td>\n",
       "      <td>30</td>\n",
       "    </tr>\n",
       "  </tbody>\n",
       "</table>\n",
       "</div>"
      ],
      "text/plain": [
       "   a   b\n",
       "0  1  10\n",
       "1  2  20\n",
       "2  3  30\n",
       "3  4  30"
      ]
     },
     "execution_count": 62,
     "metadata": {},
     "output_type": "execute_result"
    }
   ],
   "source": [
    "def expand_rows(x):\n",
    "    \"\"\" -----------------\n",
    "        Dict -> List Dict\n",
    "        -----------------\n",
    "        Given a dictionary, create a new dictionary for each\n",
    "        value in the 'a' field. \n",
    "    \"\"\"\n",
    "    a_values = [value.strip() for value in x['a'].split(',')]\n",
    "    def create_row(value):\n",
    "        y = x.copy()\n",
    "        y['a'] = value\n",
    "        return y\n",
    "    return map(create_row, a_values)\n",
    "\n",
    "pd.DataFrame(list(tz.mapcat(expand_rows, rows)))"
   ]
  }
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