title: I only want to keep the row in a dataframe with conditions
body: <p>Here is my dataframe:</p>
  
  <pre><code>zip_count[zip_count.Zipcode.apply(lambda x: x.isnumeric())]
  zip_count
  
      Zipcode Employees
  0   00728   1
  1   00926   1
  2   01027   2
  3   01028   4
  4   01040   2
  ... ... ...
  652 98121   1
  653 98144   1
  654 98296   1
  655 B1S 3   1
  656 POSTAL  2
  </code></pre>
  
  <p>I only want to keep the zipcode start with "02---", how should I do that? Thank you!</p>