title: python multidimensional list.. how to grab one dimension?
body: <p>my question is, is I have a list like the following:</p>
  
  <pre><code>someList = [[0,1,2],[3,4,5],[6,7,8]]
  </code></pre>
  
  <p>how would I get the first entry of each sublist? </p>
  
  <p>I know I could do this:</p>
  
  <pre><code>newList = []
  for entry in someList:
      newList.append(entry[0])
  </code></pre>
  
  <p>where newList would be:</p>
  
  <pre><code>[0, 3, 6]
  </code></pre>
  
  <p>But is there a way to do something like:</p>
  
  <pre><code>newList = someList[:][0] 
  </code></pre>
  
  <p>?</p>
  
  <p>EDIT:</p>
  
  <p>Efficiency is of great concern. I am actually going through a list that has over 300000 entries</p>