title: what is difference between [None] and [] in python?
body: <p>I think [None] is same as [], but in my test , maybe there is something...</p>
  
  <pre><code>&gt;&gt;&gt;print len([])
  0
  &gt;&gt;&gt;print len([None])
  1
  </code></pre>
  
  <p>when should i use the None ? and [] </p>
  
  <p>and another interesting question </p>
  
  <pre><code>&gt;&gt;&gt;c= []
  &gt;&gt;&gt;d= []
  &gt;&gt;&gt;print c is d
  False
  &gt;&gt;&gt;a= 1
  &gt;&gt;&gt;b=1
  print a is b
  True
  </code></pre>
  
  <p>why empty list's id granting that is different?</p>