title: PYTHON-Merge single elements in list with sublist
body: <p>I try to make flat list. Now I have list:</p>
  
  <pre><code>L=['aa',['bb','cc']]
  </code></pre>
  
  <p>and I try:</p>
  
  <pre><code>L=['aa',['bb','cc']]
  new=[]
  
  for i in L:
    print i
    new+=i
  
  print new
  </code></pre>
  
  <p>and I got:</p>
  
  <pre><code>'aa'
  
  ['bb','cc']
  
  ['a','a','bb','cc']
  </code></pre>
  
  <p>Why in <code>print i=0 = 'aa'</code> and in <code>new+=i i=0</code> is only 'a'?</p>
  
  <p>How i could get list <code>['aa','bb','cc']</code>?</p>