pandas_create_column_with_loop.ipynb

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   "cells": [
    {
     "cell_type": "markdown",
     "metadata": {},
     "source": [
      "# Create A Pandas Column With A For Loop\n",
      "\n",
      "- **Author:** [Chris Albon](http://www.chrisalbon.com/), [@ChrisAlbon](https://twitter.com/chrisalbon)\n",
      "- **Date:** -\n",
      "- **Repo:** [Python 3 code snippets for data science](https://github.com/chrisalbon/code_py)\n",
      "- **Note:**"
     ]
    },
    {
     "cell_type": "markdown",
     "metadata": {},
     "source": [
      "## Preliminaries"
     ]
    },
    {
     "cell_type": "code",
     "collapsed": false,
     "input": [
      "import pandas as pd\n",
      "import numpy as np"
     ],
     "language": "python",
     "metadata": {},
     "outputs": [],
     "prompt_number": 7
    },
    {
     "cell_type": "markdown",
     "metadata": {},
     "source": [
      "## Create an example dataframe"
     ]
    },
    {
     "cell_type": "code",
     "collapsed": false,
     "input": [
      "raw_data = {'student_name': ['Miller', 'Jacobson', 'Ali', 'Milner', 'Cooze', 'Jacon', 'Ryaner', 'Sone', 'Sloan', 'Piger', 'Riani', 'Ali'], \n",
      "        'test_score': [76, 88, 84, 67, 53, 96, 64, 91, 77, 73, 52, np.NaN]}\n",
      "df = pd.DataFrame(raw_data, columns = ['student_name', 'test_score'])"
     ],
     "language": "python",
     "metadata": {},
     "outputs": []
    },
    {
     "cell_type": "markdown",
     "metadata": {},
     "source": [
      "## Create a function to assign letter grades"
     ]
    },
    {
     "cell_type": "code",
     "collapsed": false,
     "input": [
      "# Create a list to store the data\n",
      "grades = []\n",
      "\n",
      "# For each row in the column,\n",
      "for row in df['test_score']:\n",
      "    # if more than a value,\n",
      "    if row > 95:\n",
      "        # Append a letter grade\n",
      "        grades.append('A')\n",
      "    # else, if more than a value,\n",
      "    elif row > 90:\n",
      "        # Append a letter grade\n",
      "        grades.append('A-')\n",
      "    # else, if more than a value,\n",
      "    elif row > 85:\n",
      "        # Append a letter grade\n",
      "        grades.append('B')\n",
      "    # else, if more than a value,\n",
      "    elif row > 80:\n",
      "        # Append a letter grade\n",
      "        grades.append('B-')\n",
      "    # else, if more than a value,\n",
      "    elif row > 75:\n",
      "        # Append a letter grade\n",
      "        grades.append('C')\n",
      "    # else, if more than a value,\n",
      "    elif row > 70:\n",
      "        # Append a letter grade\n",
      "        grades.append('C-')\n",
      "    # else, if more than a value,\n",
      "    elif row > 65:\n",
      "        # Append a letter grade\n",
      "        grades.append('D')\n",
      "    # else, if more than a value,\n",
      "    elif row > 60:\n",
      "        # Append a letter grade\n",
      "        grades.append('D-')\n",
      "    # otherwise,\n",
      "    else:\n",
      "        # Append a failing grade\n",
      "        grades.append('Failed')\n",
      "        \n",
      "# Create a column from the list\n",
      "df['grades'] = grades"
     ],
     "language": "python",
     "metadata": {},
     "outputs": [],
     "prompt_number": 22
    },
    {
     "cell_type": "code",
     "collapsed": false,
     "input": [
      "# View the new dataframe\n",
      "df"
     ],
     "language": "python",
     "metadata": {},
     "outputs": [
      {
       "html": [
        "<div style=\"max-height:1000px;max-width:1500px;overflow:auto;\">\n",
        "<table border=\"1\" class=\"dataframe\">\n",
        "  <thead>\n",
        "    <tr style=\"text-align: right;\">\n",
        "      <th></th>\n",
        "      <th>student_name</th>\n",
        "      <th>test_score</th>\n",
        "      <th>grades</th>\n",
        "    </tr>\n",
        "  </thead>\n",
        "  <tbody>\n",
        "    <tr>\n",
        "      <th>0 </th>\n",
        "      <td>   Miller</td>\n",
        "      <td> 76</td>\n",
        "      <td>      C</td>\n",
        "    </tr>\n",
        "    <tr>\n",
        "      <th>1 </th>\n",
        "      <td> Jacobson</td>\n",
        "      <td> 88</td>\n",
        "      <td>      B</td>\n",
        "    </tr>\n",
        "    <tr>\n",
        "      <th>2 </th>\n",
        "      <td>      Ali</td>\n",
        "      <td> 84</td>\n",
        "      <td>     B-</td>\n",
        "    </tr>\n",
        "    <tr>\n",
        "      <th>3 </th>\n",
        "      <td>   Milner</td>\n",
        "      <td> 67</td>\n",
        "      <td>      D</td>\n",
        "    </tr>\n",
        "    <tr>\n",
        "      <th>4 </th>\n",
        "      <td>    Cooze</td>\n",
        "      <td> 53</td>\n",
        "      <td> Failed</td>\n",
        "    </tr>\n",
        "    <tr>\n",
        "      <th>5 </th>\n",
        "      <td>    Jacon</td>\n",
        "      <td> 96</td>\n",
        "      <td>      A</td>\n",
        "    </tr>\n",
        "    <tr>\n",
        "      <th>6 </th>\n",
        "      <td>   Ryaner</td>\n",
        "      <td> 64</td>\n",
        "      <td>     D-</td>\n",
        "    </tr>\n",
        "    <tr>\n",
        "      <th>7 </th>\n",
        "      <td>     Sone</td>\n",
        "      <td> 91</td>\n",
        "      <td>     A-</td>\n",
        "    </tr>\n",
        "    <tr>\n",
        "      <th>8 </th>\n",
        "      <td>    Sloan</td>\n",
        "      <td> 77</td>\n",
        "      <td>      C</td>\n",
        "    </tr>\n",
        "    <tr>\n",
        "      <th>9 </th>\n",
        "      <td>    Piger</td>\n",
        "      <td> 73</td>\n",
        "      <td>     C-</td>\n",
        "    </tr>\n",
        "    <tr>\n",
        "      <th>10</th>\n",
        "      <td>    Riani</td>\n",
        "      <td> 52</td>\n",
        "      <td> Failed</td>\n",
        "    </tr>\n",
        "    <tr>\n",
        "      <th>11</th>\n",
        "      <td>      Ali</td>\n",
        "      <td>NaN</td>\n",
        "      <td> Failed</td>\n",
        "    </tr>\n",
        "  </tbody>\n",
        "</table>\n",
        "</div>"
       ],
       "metadata": {},
       "output_type": "pyout",
       "prompt_number": 23,
       "text": [
        "   student_name  test_score  grades\n",
        "0        Miller          76       C\n",
        "1      Jacobson          88       B\n",
        "2           Ali          84      B-\n",
        "3        Milner          67       D\n",
        "4         Cooze          53  Failed\n",
        "5         Jacon          96       A\n",
        "6        Ryaner          64      D-\n",
        "7          Sone          91      A-\n",
        "8         Sloan          77       C\n",
        "9         Piger          73      C-\n",
        "10        Riani          52  Failed\n",
        "11          Ali         NaN  Failed"
       ]
      }
     ],
     "prompt_number": 23
    }
   ],
   "metadata": {}
  }
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