title: pandas apply convert to int differences between np.int, lambda and astype()
body: <p>Given a df</p>
  
  <pre><code>df = pd.DataFrame(['0', '1', '2', '3'], columns=['a'])
  </code></pre>
  
  <p>What is the difference between using</p>
  
  <pre><code> df['b'] = df['a'].apply(np.int)
  </code></pre>
  
  <p>,</p>
  
  <pre><code>df['b'] = df['a'].apply(lambda x : int(x))
  </code></pre>
  
  <p>and</p>
  
  <pre><code>df['b'] = df['a'].astype(int)
  </code></pre>
  
  <p>? </p>
  
  <p>I'm aware that all will give the same result but are there any differences?</p>