title: accessing python 2D array
body: <p>suppose we have:</p>
  
  <pre><code>a = [[1, 2, 3], [4, 5, 6]]
  </code></pre>
  
  <p>What is the fastest way to access the array such that we get the first element in each list, other than looping.</p>
  
  <p>i would like the result to be giving me... 1,4</p>