title: How to convert a grouped pandas series to a numpy array
body: <p>The <code>df</code> below contains integers grouped by time. I’m trying to convert these to a <code>numpy</code> array.</p>
  
  <pre><code>import pandas as pd
  import numpy as np
  
  df = pd.DataFrame({
      'Time' : [1,1,1,2,2,2,3,3,3],        
      'A' : [3, 4, 5, 2, 5, 6, 1, 6, 7], 
      'B' : [2, 4, 5, 2, 5, 5, 2, 6, 5],                           
  })
  
  GA = np.array(df.groupby(['Time'])['A'].apply(np.array))
  </code></pre>
  
  <p>Intended Out:</p>
  
  <pre><code>[[ 3  4  5]
   [ 2  5  6]
   [ 1  6  7]]
  </code></pre>