title: Understanding inplace=True in pandas
body: <p>In the <code>pandas</code> library many times there is an option to change the object inplace such as with the following statement...</p>
  <pre><code>df.dropna(axis='index', how='all', inplace=True)
  </code></pre>
  <p>I am curious what is being returned as well as how the object is handled when <code>inplace=True</code> is passed vs. when <code>inplace=False</code>.</p>
  <p>Are all operations modifying <code>self</code> when <code>inplace=True</code>? And when <code>inplace=False</code> is a new object created immediately such as <code>new_df = self</code> and then <code>new_df</code> is returned?</p>
  <hr />
  <p><sub>If you are trying to close a question where someone should use <code>inplace=True</code> and hasn't, consider <a href="https://stackoverflow.com/questions/37593550">replace() method not working on Pandas DataFrame</a> instead.</sub></p>