Converting pandas dataframe to structured arrays

Question

I have the following pandas dataframe

import pandas as pd
a = [2.5,3.3]
b = [3.6,3.9]
D = {\'A\': a, \'B\': b}

which gives me

Answer 1

np.rec.fromrecords(list(zip(df.melt().variable,df.melt().value)))
Out[531]: 
rec.array([('A',  2.5), ('A',  3.3), ('B',  3.6), ('B',  3.9)], 
          dtype=[('f0', '