title: Difference between `groupby.unique` and `groupby.first` functions
body: <p>I am trying to combine two neighborhood names with the same postal code in a dataframe.</p>
  
  <p>Initially I used <code>groupby.unique()</code> function but it returns a <code>ndarray</code> in each cell. I later tried <code>groupby.first()</code> function which returns the value of the repeated postal code.</p>
  
  <pre><code>PCode =pd.DataFrame({'PostalCode':['M4A','M5A','M5A'],'Borough':['North York','Downtown Toronto','Downtown Toronto'],'Neighbourhood':['Victoria Village','Harbourfront','Regent Park']})
  PCode.groupby('PostalCode')['PostalCode'].unique()
  PCode.groupby('PostalCode')['PostalCode'].first()
  </code></pre>
  
  <p>I wonder whether there is a way to extract the postal code out of the returned <code>ndarray</code> for the <code>groupby.unique()</code> function to produce exactly the same result as when using the <code>groupby.first()</code> function.</p>