title: Find indices of duplicate rows in pandas DataFrame
body: <p>What is the pandas way of finding the indices of identical rows within a given DataFrame without iterating over individual rows?</p>
  
  <p>While it is possible to find all unique rows with <code>unique = df[df.duplicated()]</code> and then iterating over the unique entries with <code>unique.iterrows()</code> and extracting the indices of equal entries with help of <code>pd.where()</code>, what is the pandas way of doing it?</p>
  
  <p><strong>Example:</strong>
  Given a DataFrame of the following structure:</p>
  
  <pre><code>  | param_a | param_b | param_c
  1 | 0       | 0       | 0
  2 | 0       | 2       | 1
  3 | 2       | 1       | 1
  4 | 0       | 2       | 1
  5 | 2       | 1       | 1
  6 | 0       | 0       | 0
  </code></pre>
  
  <p>Output:</p>
  
  <pre><code>[(1, 6), (2, 4), (3, 5)]
  </code></pre>