Add indexed column to DataFrame with pandas

Question

I\'m a beginning pandas user, and after studying the documentation I still can\'t find a straightforward way to do the following.

I have a DataFrame with a pandas.DateR

Answer 1

df['C'] = df2['C'] should also work in this case.

Answer 2

Do df.join(df2):

http://pandas.pydata.org/pandas-docs/stable/merging.html#joining-on-index