~python

import pandas as pd

brech = pd.DataFrame({'base': [0, 1, 2, 3, 4],
               'min': [0, 3, 4, 8, 32],
               'max': [2, 3, 7, 31, 92]})
datos = pd.DataFrame({'dias': [-10, -12, -13, 8, 5, 15, 20, 0, 3, 10, 40, 31]})

dias    base
-10     nan
-12     nan
-13     nan
8       3
5       2
15      3
20      3
0       0
3       1
10      3
40      4

datos['base'] = datos['dias'].apply(lambda x: [brech['base']
                                   if x > brech.iloc[i,1] and x < brech.iloc[i,2] else ""])