DataFrame.to_csv bug: headers mis-aligned
pandas version: 0.4.0 from pypi

The problem is that there is no header for the index column:

In [1]: import pandas

In [2]: d = pandas.DataFrame(randn(3, 2), range(3), ['a', 'b'])

In [3]: d.to_csv('tmp.csv')

In [4]: cat tmp.csv
a,b
0,-0.244543341458,-1.50542482731
1,-1.02524916375,0.279887233706
2,0.0657877607121,-0.786951623121
