title: turn column of numbers into comma separated list
body: <p>Hi I have data like this</p>
  
  <pre><code>40
  50
  70
  </code></pre>
  
  <p>I want output like this:
  40,50,70</p>
  
  <p>I have tried:</p>
  
  <pre><code>from sys import argv
  script, pos_file, output = argv
  positions = []
  with open(pos_file) as f:
     for x in f:
        positions.append(x)
  print positions
  </code></pre>
  
  <p>It gives me a list like '40\n', '50\n', '70\n' so it is treating the numbers as strings and printing the line deliminator \n.  How can I modify this code to do what I want?</p>
  
  <p>Thanks.</p>