title: Remove non-numeric rows in one column with pandas
body: <p>There is a dataframe like the following, and it has one unclean column 'id' which it sholud be numeric column</p>
  
  <pre><code>id, name
  1,  A
  2,  B
  3,  C
  tt, D
  4,  E
  5,  F
  de, G
  </code></pre>
  
  <p>Is there a concise way to remove the rows because tt and de are not numeric values</p>
  
  <pre><code>tt,D
  de,G
  </code></pre>
  
  <p>to make the dataframe clean?</p>
  
  <pre><code>id, name
  1,  A
  2,  B
  3,  C
  4,  E
  5,  F
  </code></pre>