title: Adding an np.array as a column in a pandas.DataFrame
body: <p>I have a pandas data frame and a numpy nd array with one dimension. Effectively it is a list. </p>
  
  <p>How do I add a new column to the DataFrame with the values from the array?</p>
  
  <p><code>test['preds'] = preds</code> gives <code>SettingWithCopyWarning</code>
  And a warning:</p>
  
  <blockquote>
    <p>A value is trying to be set on a copy of a slice from a DataFrame.
    Try using .loc[row_indexer,col_indexer] = value instead</p>
  </blockquote>
  
  <p>And when I try <code>pd.DataFrame({test,preds})</code> I get <code>TypeError: unhashable type: 'list'</code></p>