title: Pandas concat yields ValueError: Plan shapes are not aligned
body: <p>In pandas, I am attempting to concatenate a set of dataframes and I am getting this error:</p>
  <pre><code>ValueError: Plan shapes are not aligned
  </code></pre>
  <p>My understanding of <code>.concat()</code> is that it will join where columns are the same, but for those that it can't find it will fill with NA. This doesn't seem to be the case here.</p>
  <p>Here's the concat statement:</p>
  <pre><code>dfs = [npo_jun_df, npo_jul_df,npo_may_df,npo_apr_df,npo_feb_df]
  alpha = pd.concat(dfs)
  </code></pre>