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Created January 7, 2013 08:50
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understanding assignment.ipynb
{
"metadata": {
"name": "understanding assignment"
},
"nbformat": 3,
"nbformat_minor": 0,
"worksheets": [
{
"cells": [
{
"cell_type": "code",
"collapsed": false,
"input": [
"import pandas as pd"
],
"language": "python",
"metadata": {},
"outputs": [],
"prompt_number": 1
},
{
"cell_type": "code",
"collapsed": false,
"input": [
"df = pd.DataFrame(randn(6,3),columns = list('ABC'))"
],
"language": "python",
"metadata": {},
"outputs": [],
"prompt_number": 21
},
{
"cell_type": "code",
"collapsed": false,
"input": [
"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>A</th>\n",
" <th>B</th>\n",
" <th>C</th>\n",
" </tr>\n",
" </thead>\n",
" <tbody>\n",
" <tr>\n",
" <td><strong>0</strong></td>\n",
" <td>-0.031630</td>\n",
" <td>-1.867797</td>\n",
" <td> 1.264133</td>\n",
" </tr>\n",
" <tr>\n",
" <td><strong>1</strong></td>\n",
" <td>-0.135349</td>\n",
" <td>-0.957986</td>\n",
" <td>-0.054713</td>\n",
" </tr>\n",
" <tr>\n",
" <td><strong>2</strong></td>\n",
" <td> 0.337048</td>\n",
" <td>-0.383348</td>\n",
" <td>-1.991538</td>\n",
" </tr>\n",
" <tr>\n",
" <td><strong>3</strong></td>\n",
" <td> 1.009888</td>\n",
" <td>-0.779377</td>\n",
" <td>-1.481212</td>\n",
" </tr>\n",
" <tr>\n",
" <td><strong>4</strong></td>\n",
" <td>-0.962852</td>\n",
" <td> 0.129088</td>\n",
" <td>-0.010233</td>\n",
" </tr>\n",
" <tr>\n",
" <td><strong>5</strong></td>\n",
" <td>-0.640262</td>\n",
" <td> 0.848540</td>\n",
" <td> 1.025306</td>\n",
" </tr>\n",
" </tbody>\n",
"</table>\n",
"</div>"
],
"output_type": "pyout",
"prompt_number": 22,
"text": [
" A B C\n",
"0 -0.031630 -1.867797 1.264133\n",
"1 -0.135349 -0.957986 -0.054713\n",
"2 0.337048 -0.383348 -1.991538\n",
"3 1.009888 -0.779377 -1.481212\n",
"4 -0.962852 0.129088 -0.010233\n",
"5 -0.640262 0.848540 1.025306"
]
}
],
"prompt_number": 22
},
{
"cell_type": "code",
"collapsed": false,
"input": [
"df['D']=0.0"
],
"language": "python",
"metadata": {},
"outputs": [],
"prompt_number": 33
},
{
"cell_type": "code",
"collapsed": false,
"input": [
"key = 3*[1]+3*[2]"
],
"language": "python",
"metadata": {},
"outputs": [],
"prompt_number": 34
},
{
"cell_type": "code",
"collapsed": false,
"input": [
"df['key']=key\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>A</th>\n",
" <th>B</th>\n",
" <th>C</th>\n",
" <th>D</th>\n",
" <th>key</th>\n",
" </tr>\n",
" </thead>\n",
" <tbody>\n",
" <tr>\n",
" <td><strong>0</strong></td>\n",
" <td>-0.031630</td>\n",
" <td>-1.867797</td>\n",
" <td> 1.264133</td>\n",
" <td> 0</td>\n",
" <td> 1</td>\n",
" </tr>\n",
" <tr>\n",
" <td><strong>1</strong></td>\n",
" <td>-0.135349</td>\n",
" <td>-0.957986</td>\n",
" <td>-0.054713</td>\n",
" <td> 0</td>\n",
" <td> 1</td>\n",
" </tr>\n",
" <tr>\n",
" <td><strong>2</strong></td>\n",
" <td> 0.337048</td>\n",
" <td>-0.383348</td>\n",
" <td>-1.991538</td>\n",
" <td> 0</td>\n",
" <td> 1</td>\n",
" </tr>\n",
" <tr>\n",
" <td><strong>3</strong></td>\n",
" <td> 1.009888</td>\n",
" <td>-0.779377</td>\n",
" <td>-1.481212</td>\n",
" <td> 0</td>\n",
" <td> 2</td>\n",
" </tr>\n",
" <tr>\n",
" <td><strong>4</strong></td>\n",
" <td>-0.962852</td>\n",
" <td> 0.129088</td>\n",
" <td>-0.010233</td>\n",
" <td> 0</td>\n",
" <td> 2</td>\n",
" </tr>\n",
" <tr>\n",
" <td><strong>5</strong></td>\n",
" <td>-0.640262</td>\n",
" <td> 0.848540</td>\n",
" <td> 1.025306</td>\n",
" <td> 0</td>\n",
" <td> 2</td>\n",
" </tr>\n",
" </tbody>\n",
"</table>\n",
"</div>"
],
"output_type": "pyout",
"prompt_number": 35,
"text": [
" A B C D key\n",
"0 -0.031630 -1.867797 1.264133 0 1\n",
"1 -0.135349 -0.957986 -0.054713 0 1\n",
"2 0.337048 -0.383348 -1.991538 0 1\n",
"3 1.009888 -0.779377 -1.481212 0 2\n",
"4 -0.962852 0.129088 -0.010233 0 2\n",
"5 -0.640262 0.848540 1.025306 0 2"
]
}
],
"prompt_number": 35
},
{
"cell_type": "raw",
"metadata": {},
"source": [
"this doesn't work:"
]
},
{
"cell_type": "code",
"collapsed": false,
"input": [
"df[df.key==1]['D'] = 1\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>A</th>\n",
" <th>B</th>\n",
" <th>C</th>\n",
" <th>D</th>\n",
" <th>key</th>\n",
" </tr>\n",
" </thead>\n",
" <tbody>\n",
" <tr>\n",
" <td><strong>0</strong></td>\n",
" <td>-0.031630</td>\n",
" <td>-1.867797</td>\n",
" <td> 1.264133</td>\n",
" <td> 0</td>\n",
" <td> 1</td>\n",
" </tr>\n",
" <tr>\n",
" <td><strong>1</strong></td>\n",
" <td>-0.135349</td>\n",
" <td>-0.957986</td>\n",
" <td>-0.054713</td>\n",
" <td> 0</td>\n",
" <td> 1</td>\n",
" </tr>\n",
" <tr>\n",
" <td><strong>2</strong></td>\n",
" <td> 0.337048</td>\n",
" <td>-0.383348</td>\n",
" <td>-1.991538</td>\n",
" <td> 0</td>\n",
" <td> 1</td>\n",
" </tr>\n",
" <tr>\n",
" <td><strong>3</strong></td>\n",
" <td> 1.009888</td>\n",
" <td>-0.779377</td>\n",
" <td>-1.481212</td>\n",
" <td> 0</td>\n",
" <td> 2</td>\n",
" </tr>\n",
" <tr>\n",
" <td><strong>4</strong></td>\n",
" <td>-0.962852</td>\n",
" <td> 0.129088</td>\n",
" <td>-0.010233</td>\n",
" <td> 0</td>\n",
" <td> 2</td>\n",
" </tr>\n",
" <tr>\n",
" <td><strong>5</strong></td>\n",
" <td>-0.640262</td>\n",
" <td> 0.848540</td>\n",
" <td> 1.025306</td>\n",
" <td> 0</td>\n",
" <td> 2</td>\n",
" </tr>\n",
" </tbody>\n",
"</table>\n",
"</div>"
],
"output_type": "pyout",
"prompt_number": 36,
"text": [
" A B C D key\n",
"0 -0.031630 -1.867797 1.264133 0 1\n",
"1 -0.135349 -0.957986 -0.054713 0 1\n",
"2 0.337048 -0.383348 -1.991538 0 1\n",
"3 1.009888 -0.779377 -1.481212 0 2\n",
"4 -0.962852 0.129088 -0.010233 0 2\n",
"5 -0.640262 0.848540 1.025306 0 2"
]
}
],
"prompt_number": 36
},
{
"cell_type": "raw",
"metadata": {},
"source": [
"this does: (why only this way?)"
]
},
{
"cell_type": "code",
"collapsed": false,
"input": [
"df.D[df.key==1]=3.4\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>A</th>\n",
" <th>B</th>\n",
" <th>C</th>\n",
" <th>D</th>\n",
" <th>key</th>\n",
" </tr>\n",
" </thead>\n",
" <tbody>\n",
" <tr>\n",
" <td><strong>0</strong></td>\n",
" <td>-0.031630</td>\n",
" <td>-1.867797</td>\n",
" <td> 1.264133</td>\n",
" <td> 3.4</td>\n",
" <td> 1</td>\n",
" </tr>\n",
" <tr>\n",
" <td><strong>1</strong></td>\n",
" <td>-0.135349</td>\n",
" <td>-0.957986</td>\n",
" <td>-0.054713</td>\n",
" <td> 3.4</td>\n",
" <td> 1</td>\n",
" </tr>\n",
" <tr>\n",
" <td><strong>2</strong></td>\n",
" <td> 0.337048</td>\n",
" <td>-0.383348</td>\n",
" <td>-1.991538</td>\n",
" <td> 3.4</td>\n",
" <td> 1</td>\n",
" </tr>\n",
" <tr>\n",
" <td><strong>3</strong></td>\n",
" <td> 1.009888</td>\n",
" <td>-0.779377</td>\n",
" <td>-1.481212</td>\n",
" <td> 0.0</td>\n",
" <td> 2</td>\n",
" </tr>\n",
" <tr>\n",
" <td><strong>4</strong></td>\n",
" <td>-0.962852</td>\n",
" <td> 0.129088</td>\n",
" <td>-0.010233</td>\n",
" <td> 0.0</td>\n",
" <td> 2</td>\n",
" </tr>\n",
" <tr>\n",
" <td><strong>5</strong></td>\n",
" <td>-0.640262</td>\n",
" <td> 0.848540</td>\n",
" <td> 1.025306</td>\n",
" <td> 0.0</td>\n",
" <td> 2</td>\n",
" </tr>\n",
" </tbody>\n",
"</table>\n",
"</div>"
],
"output_type": "pyout",
"prompt_number": 39,
"text": [
" A B C D key\n",
"0 -0.031630 -1.867797 1.264133 3.4 1\n",
"1 -0.135349 -0.957986 -0.054713 3.4 1\n",
"2 0.337048 -0.383348 -1.991538 3.4 1\n",
"3 1.009888 -0.779377 -1.481212 0.0 2\n",
"4 -0.962852 0.129088 -0.010233 0.0 2\n",
"5 -0.640262 0.848540 1.025306 0.0 2"
]
}
],
"prompt_number": 39
},
{
"cell_type": "code",
"collapsed": false,
"input": [],
"language": "python",
"metadata": {},
"outputs": []
}
],
"metadata": {}
}
]
}
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