def add_dict_b_to_dict_a(dict_a, dict_b):
    for key, value in dict_b.items():
        dict_a[key] = dict_a.get(key, 0) + value
    return dict_a


if __name__ == "__main__":
    # for example
    # source: https://stackoverflow.com/a/35689816
    from functools import reduce

    a = {"a": 10, "b": 20}
    b = {"b": 22, "c": 60}
    c = {"b": 1}
    res = reduce(add_dict_b_to_dict_a, [a, b, c], dict())
    print(res)