title: Index objects in pandas--why pd.columns returns index rather than list
body: <p>Coming from R background, I find the (very high) use of <code>Index</code> objects in pandas a little disconcerting. For example, if <code>train</code> is a pandas DataFrame, is there some special reason why <code>train.columns</code> should return an <code>Index</code> rather than a list? What purpose would additionally be served if it is an <code>Index</code> object? As per the definition of <code>pandas.Index</code>, it is the  basic object storing axis labels for all pandas objects. While <code>train.index.values</code> does return the row labels (axis=0), how can I get column labels or columns names from <code>pandas.index</code>? In this question unlike in an earlier question, I have a specific example in mind.</p>