title: Python 3 How to check if a value is already in a list in a list
body: <p>I have a list of lists in my Python 3:</p>
  <pre><code>mylist = [[a,x,x][b,x,x][c,x,x]]
  </code></pre>
  <p>(x is just some data)</p>
  <p>I have my code which does that:</p>
  <pre><code>for sublist in mylist:
      if sublist[0] == a:
          sublist[1] = sublist[1]+1
          break
  </code></pre>
  <p>now I want to add an entry, if there is any sublistentry ==a</p>
  <p>How can I do that?</p>