title: Count frequency of values in pandas DataFrame column
body: <p>I want to count number of times each values is appearing in dataframe.</p>
  
  <p>Here is my dataframe - <code>df</code>:</p>
  
  <pre><code>    status
  1     N
  2     N
  3     C
  4     N
  5     S
  6     N
  7     N
  8     S
  9     N
  10    N
  11    N
  12    S
  13    N
  14    C
  15    N
  16    N
  17    N
  18    N
  19    S
  20    N
  </code></pre>
  
  <p>I want to dictionary of counts: </p>
  
  <p>ex. <code>counts = {N: 14, C:2, S:4}</code></p>
  
  <p>I have tried <code>df['status']['N']</code> but it gives <code>keyError</code> and also <code>df['status'].value_counts</code> but no use.   </p>