title: Join strings contained in lists
body: <p>I would like to create a list of joined strings, where the joined strings were once lists within another list. I suppose I could use a for-loop, but was wondering if there is a better way to accomplish this. See below for an example and expected output.</p>
  
  <p>Starting list:</p>
  
  <pre><code>x = [
        ['2019','4'],
        ['2019','3'],
        ['2019','2'],
        ['2019','1']
      ]
  </code></pre>
  
  <p>Expected output:</p>
  
  <pre><code>[
   '20194',
   '20193',
   '20192',
   '20191'
  ]
  </code></pre>