title: How do I get a list of indices of non zero elements in a list?
body: <p>I have a list that will always contain only ones and zeroes.
  I need to get a list of the non-zero indices of the list:</p>
  
  <pre><code>a = [0, 1, 0, 1, 0, 0, 0, 0]
  b = []
  for i in range(len(a)):
      if a[i] == 1:  b.append(i)
  print b
  </code></pre>
  
  <p>What would be the 'pythonic' way of achieving this ?</p>