title: Does the extra comma at the end of a dictionary, list or set has any special meaning in Python?
body: <p>I noticed by chance that adding an extra separator <em>comma</em> at the end of a <em>list</em>, <em>dictionary</em> or <em>set</em> is syntactically correct and does not seem to add anything to the data structure:</p>
  <pre><code>In [1]: d1 = {'a': 1, 'b': 2}
  
  In [2]: d2 = {'c': 10, 'd': 20,}
  
  In [3]: d1
  Out[3]: {'a': 1, 'b': 2}
  
  In [4]: d2
  Out[4]: {'c': 10, 'd': 20}
  </code></pre>
  <p>Does it have any special meaning or usage?<br />
  The only one I found is to explicit a data structure during an initialization:</p>
  <pre><code>In [14]: r = (1)
  
  In [15]: r
  Out[15]: 1
  
  In [16]: r = (1,)
  
  In [17]: r
  Out[17]: (1,)
  </code></pre>