title: counting 2D list in python
body: <p>my 2D list just like:</p>
  <pre><code>log = [[time1, 'aaa', '123.123.123.123'], [time2, 'def', '123.123.123.123'], [time3, 'aaa', '123.123.123.123'], [time4, 'bbb', '123.123.123.123'], [time5, 'bbb', '123.123.123.123']]
  </code></pre>
  <p>what I want is, the output below by using for loop:</p>
  <pre><code>aaa: 2
  def: 1
  bbb: 2
  </code></pre>
  <p>how can I count the specific col in a 2D list by loop?</p>