#INPUT
#   1-A  1-B  2-A  5-B
#0    1    3    3    2
#1    2    4    4    7

#1-A: person id is 1, expense category is A
#rows are months
#calculate total expense per person per month

#OUTPUT
#   1  2  5
#0  4  3  2
#1  6  4  7


import pandas as pd

d = {'1-A': [1, 2], '1-B': [3, 4], '2-A': [3, 4], '5-B': [2, 7]}
df = pd.DataFrame(data=d)

df1 = df.groupby(lambda x: x.split('-')[0], axis=1).sum()