title: why I can't append directly after a split in python
body: <pre><code>test = "123213 32543543 52354 234 34"
  a = test.split().append("sd")
  print (a)
  </code></pre>
  
  <p>The above code will give me a None in output, while the following code will output a list:</p>
  
  <pre><code>test = "123213 32543543 52354 234 34"
  a = test.split()
  a.append("sd")
  print (a)
  </code></pre>
  
  <p>Can anyone explain it? Thanks.</p>