title: Exclude null values in map function of Python3
body: <p>I am using <code>map</code> to process a list in Python3.6:</p>
  
  <pre><code>def calc(num):
      if num &gt; 5:
          return None
      return num * 2
  
  
  r = map(lambda num: clac(num), range(1, 10))
  print(list(r))
  
  # =&gt; [2, 4, 6, 8, 10, None, None, None, None]
  </code></pre>
  
  <p>The result I expect is: <code>[2, 4, 6, 8, 10]</code>.</p>
  
  <p>Of course, I can use <code>filter</code> to handle <code>map</code> result. But is there a way for <code>map</code> to return directly to the result I want?</p>