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POPivoting pandas DataFrame -- AssertionError: Index length did not match values
 

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  1. POPivoting pandas DataFrame -- AssertionError: Index length did not match values
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    <p>I have a <em>pandas.DataFrame</em> that won't pivot the way I expect. While <code>pivot_table</code> properly arranges everything, the fact that it uses aggregate functions to get there is off-putting. In addition, <code>pivot_table</code> seems to return an unnecessarily complex object rather than a flat data frame.</p> <p>Consider the following example</p> <pre><code>import pandas as pd df = pd.DataFrame({'firstname':['Jon']*3+['Amy']*2, 'lastname':['Cho']*3+['Frond']*2, 'vehicle':['bike', 'car', 'plane','bike','plane'], 'weight':[81.003]*3+[65.6886]*2, 'speed':[29.022, 95.1144, 302.952, 27.101, 344.2],}) df.set_index(['firstname','lastname','weight']) print('------ Unnecessary pivot_table does averaging ------') print(pd.pivot_table(df, values='speed', rows='firstname','lastname','weight'], cols='vehicle')) print('------ pivot method dies ------') print(df.pivot( index=['firstname','lastname','weight'], columns='vehicle', values='speed')) </code></pre> <p>The <code>pivot_table</code> results are</p> <pre><code>vehicle bike car plane firstname lastname weight Amy Frond 65.6886 27.101 NaN 344.200 Jon Cho 81.0030 29.022 95.1144 302.952 </code></pre> <p>Is there a way to get <code>pivot</code> to give essentially the same output as the <code>pivot_table</code> command did (but hopefully flatter and neater)? Failing that, how do I flatten the output of <code>pivot_table</code>? What I want as output is something more like this:</p> <pre><code>firstname lastname weight bike car plane Amy Frond 65.6886 27.101 NaN 344.200 Jon Cho 81.0030 29.022 95.1144 302.952 </code></pre>
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    1. COWhat does the desired dataframe look like?
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    2. COIf you want a flat dataframe, just do ``.reset_index()`` on the result of pivot_table.
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