title: Using multiple ranges with the for-loop in PYTHON
body: <p>I don't understand of using the multiple ranges in the for-loop as follows.</p>
  
  <pre><code>for n in range(1,21) + range(30,100,10):
     # do something
  </code></pre>
  
  <p>I googled but still not find out. Any help would be appreciated. </p>