title: Using DataFrame.ix with a tuple index in Pandas
body: <p>I have a bunch of Pandas code that uses tuples as indices. I've recently come across the need to access an individual element of a DataFrame with <code>DataFrame.ix</code>, which is getting confused by the tuples. It seems to think my tuple is a sequence of keys I want to access, not a single keys (which happens to be a sequence) that I want to access. How can I extract an individual row for which a tuple is the key?</p>
  
  <p>Perhaps this is a cautionary tale not to use sequences in a Pandas index, but in my case it's too late.</p>
  
  <pre><code>import string, pandas as pd, numpy as np
  
  bar = pd.DataFrame(np.random.random((8,2)))
  bar.columns = ['col1', 'col2']
  bar.index = list(string.ascii_lowercase)[:8]
  print bar
  print bar.iloc[0].name
  print bar.ix[bar.iloc[0].name]
  
  bar.index = [tuple(list(string.ascii_lowercase)[i:i+3]) for i in range(8)]
  print bar.iloc[0].name
  print bar.ix[bar.iloc[0].name] # Fails with `KeyError: 'a'`
  </code></pre>