title: Python: Removing Rows on Count condition
body: <p>I have a problem filtering a <code>pandas</code> dataframe.</p>
  
  <pre><code>city 
  NYC 
  NYC 
  NYC 
  NYC 
  SYD 
  SYD 
  SEL 
  SEL
  ...
  
  df.city.value_counts()
  </code></pre>
  
  <p>I would like to <strong>remove rows of cities that has less than 4 count frequency</strong>, which would be SYD and SEL for instance.</p>
  
  <p>What would be the way to do so without manually dropping them city by city?</p>