title: Combine two lists without duplicate values
body: <pre><code>list1 = ["palani", "samy","be"]
  list2 = ["palani", "samys","be"]
  
  def find_common(list1,list2):
      for x in list1:
        for y in list2:
          if x == y :
            list2.remove(x) 
  
  
      print" unique string 1:",list1
      print" unique string 2:",list2
      print" combained string 2:",list1.append(list2)
  
  
  find_common(list1,list2)
  </code></pre>
  
  <p><a href="https://i.stack.imgur.com/TocPl.png" rel="noreferrer"><img src="https://i.stack.imgur.com/TocPl.png" alt="enter image description here"></a></p>
  
  <p>Why am I getting <code>None</code>?</p>