title: get dataframe row count based on conditions
body: <p>I want to get the count of dataframe rows based on conditional selection. I tried the following code.</p>
  
  <pre><code>print df[(df.IP == head.idxmax()) &amp; (df.Method == 'HEAD') &amp; (df.Referrer == '"-"')].count()
  </code></pre>
  
  <p>output:</p>
  
  <pre><code>IP          57
  Time        57
  Method      57
  Resource    57
  Status      57
  Bytes       57
  Referrer    57
  Agent       57
  dtype: int64
  </code></pre>
  
  <p>The output shows the count for each an every column in the dataframe. Instead I need to get a single count where all of the above conditions satisfied? How to do this? If you need more explanation about my dataframe please let me know.</p>