title: efficient python array to numpy array conversion
body: <p>I get a big array (image with 12 Mpix) in the array format from the python standard lib.
  Since I want to perform operations on those array, I wish to convert it to a numpy array.
  I tried the following:</p>
  
  <pre><code>import numpy
  import array
  from datetime import datetime
  test = array.array('d', [0]*12000000)
  t = datetime.now()
  numpy.array(test)
  print datetime.now() - t
  </code></pre>
  
  <p>I get a result between one or two seconds: equivalent to a loop in python.</p>
  
  <p>Is there a more efficient way of doing this conversion?</p>