title: Get first item of every sublist of list in Python
body: <p>I have the following string which is a list of lists:</p>
  
  <pre><code>"ID":[[310.5,1.1612828],[310.0,15.0],[310.0,2.9755309],[309.5,30.0]]
  </code></pre>
  
  <p>I want to grab all the first values of each list into a <code>variable</code>, so the output should be in this case</p>
  
  <pre><code>print variable
  </code></pre>
  
  <p>expected output:</p>
  
  <pre><code>310.5
  310.0
  310.0
  309.5
  </code></pre>