title: Add or update pandas dataframe from list of value
body: <p>I have a dataframe</p>
  
  <pre><code>&gt;&gt;&gt; df
    name  count
  0    a      1
  1    b      2
  2    c      0
  </code></pre>
  
  <p>I want to update the value using this list</p>
  
  <pre><code> l = ['a','b','d']
  </code></pre>
  
  <p>So my updated df should look like this</p>
  
  <pre><code>&gt;&gt;&gt; df
    name  count
  0    a      2
  1    b      3
  2    c      0
  3    d      1
  </code></pre>
  
  <p>Only way I can think of is using loop. Can you people suggest any other way.
  Thanks</p>