title: Python - read_csv
body: <p>I am storing a 3D numpy array in a pandas DataFrame "df" cell :</p>
  
  <pre><code>arr =np.array([[[1,2],[1,3]],[[1,2],[2, 3]]])
  
  df.at[0,'column_A'] = arr #first row, col A
  </code></pre>
  
  <p>I save the csv file with :</p>
  
  <pre><code>df.to_csv("dataframe", sep='\t')
  </code></pre>
  
  <p>I then load it with:</p>
  
  <pre><code>df2 = pd.read_csv("dataframe", sep='\t')
  </code></pre>
  
  <p>However, the array loaded is now a string :
  <code>'[[[1 2]\n  [1 3]]\n\n [[1 2]\n  [2 3]]]'</code></p>
  
  <p>How can I get back the original array ?
  Is there something wrong in the way I am saving the csv ?
  Thanks !</p>