title: How to iterate over MultiIndex levels in Pandas?
body: <p>I often have MultiIndex indices and I'd like to iterate over groups where higher level indices are equal. It basically looks like</p>
  
  <pre><code>from random import choice
  import pandas as pd
  N = 100
  df = pd.DataFrame([choice([1, 2, 3]) for _ in range(N)],
                    columns=["A"],
                    index=pd.MultiIndex.from_tuples([(choice("ab"), choice("cd"), choice("de")) 
                                                     for _ in range(N)]))
  
  for idx in zip(df.index.get_level_values(0), df.index.get_level_values(1)):
      df_select = df.ix[idx]
  </code></pre>
  
  <p>Is there a way to do the for loop iteration more neatly?</p>