my_dict = {'A': [-1, -1, -1], 'B': [-1, -1, -1], 'C': [0, 0, 1]}
my_list = ['A', 'C']
l = []
for v in zip(*(my_dict[x] for x in my_list)):
    l += [sum(v) / len(v)]
How to sum two lists items in python