title: How to do 2D slicing?
body: <p>I'm trying to do what I think should be simple:</p>
  
  <p>I make a 2D list:</p>
  
  <pre><code>a = [[1,5],[2,6],[3,7]]
  </code></pre>
  
  <p>and I want to slide out the first <code>column</code> and tried:</p>
  
  <p>1)</p>
  
  <pre><code>a[:,0]
  ...
  TypeError: list indices must be integers or slices, not tuple
  </code></pre>
  
  <p>2)</p>
  
  <pre><code>a[:,0:1]
  ...
  TypeError: list indices must be integers or slices, not tuple
  </code></pre>
  
  <p>3)</p>
  
  <pre><code>a[:][0]
  [1, 5]
  </code></pre>
  
  <p>4)</p>
  
  <pre><code>a[0][:]
  [1, 5]
  </code></pre>
  
  <p>5) got it but is this the way to do it?</p>
  
  <pre><code> aa[0] for aa in a
  </code></pre>
  
  <p>Using <code>numpy</code> it would be easy but what is the Python way?</p>