pandas DataFrame diagonal
You could do something like this:
In [16]:midx = pd.MultiIndex.from_tuples(list(zip(df.index,df.columns)))pd.DataFrame(data=np.diag(df), index=midx)Out[16]: 0A a 2B b 2C c 3np.diag will give you the diagonal values as a np array, you can then construct the multiindex by zipping the index and columns and pass this as the desired index in the DataFrame ctor.
Actually the complex multiindex generation doesn't need to be so complicated:
In [18]:pd.DataFrame(np.diag(df), index=[df.index, df.columns])Out[18]: 0A a 2B b 2C c 3But johnchase's answer is neater