title: How to convert number mixed with character to integer in pandas
body: <p>I want to convert a columns where the elements have a type liked number mixed with character, and I want to convert the column to <code>Integer</code> type.</p>
  
  <p><code>Input:</code></p>
  
  <pre><code>df = pd.DataFrame({'id':['Q001','Q021']})
  </code></pre>
  
  <p><code>Output:</code></p>
  
  <pre><code>    id
  0   Q001
  1   Q021
  </code></pre>
  
  <p><code>Expected</code>:</p>
  
  <pre><code>    id  idInt
  0   Q001    1
  1   Q021    21
  </code></pre>