title: Dataframe replace Values with non matching indices
body: <p>I have two similar dataframe with some equal columns (not values). The idea is to update <code>df1['column1','column2]</code> with values by <code>df2['column1','column2']</code>. Indices are different, so simple:</p>
  <pre><code>df1.update(df2)
  </code></pre>
  <p>will not work properly.
  I found the instruction in internet how to make it with non matching indices:</p>
  <pre><code>col = 'id'
  cols_to_replace = ['column1', 'column2']
  df1.loc[df1[col].isin(df2[col]), cols_to_replace] = df2.loc[df2[col].isin(df1[col]),cols_to_replace].values
  </code></pre>
  <p>the problem with that code: df1 and df2 must be sorted equally by 'id'. Otherwise, you will get very strange result for your surprise!</p>
  <p>I am curious if there is better solution for the task?</p>