title: python class behaves like dictionary-or-list-data-like
body: <p>In python3 console, input those:</p>
  
  <pre><code>&gt;&gt;&gt; import sys
  &gt;&gt;&gt; sys.version_info
  sys.version_info(major=3, minor=4, micro=3, releaselevel='final', serial=0)
  &gt;&gt;&gt; type(sys.version_info)  # this is class type
  &lt;class 'sys.version_info'&gt;
  &gt;&gt;&gt; sys.version_info[0:2]  # ?? But it acts like a list-data-like
  (3, 4)
  </code></pre>
  
  <p>My questions are:</p>
  
  <ol>
  <li>How can a class act like dictionary-or-list-data-like? </li>
  <li>May give an example to construct a class like this? </li>
  <li>Is there some documentation about
  this?</li>
  </ol>