title: non-inplace version of extend operator in python
body: <p>What's a pithy pythonic non-inplace version of extend? I'm tired of writing</p>
  
  <pre><code>x = [ 1,2,3 ]
  x.extend([4,5])
  f(x)
  </code></pre>
  
  <p>Just want:</p>
  
  <pre><code> f( x.extend( [4,5], inplace=False ) )
  </code></pre>
  
  <p>or whatever    </p>