from functools import reduce

def str2num(s): return int(s)

def calc(exp): ss = exp.split('+') ns = map(str2num, ss) return reduce(lambda acc, x: acc + x, ns)

def main(): r = calc('100 + 200 + 345') print('100 + 200 + 345 =', r) r = calc('99 + 88 + 7') print('99 + 88 + 7 =', r)

main()