如何合并和求和两个嵌套字典的值并保留不存在的键:值对

dict1 = {'a': {'x': 1, 'y': 2}, 'b': {'x': 3, 'y': 4}}
dict2 = {'a': {'x': 5, 'z': 6}, 'c': {'x': 7, 'y': 8}}

result = {}

# 遍历dict1的键值对
for key1, value1 in dict1.items():
    # 将键值对添加到result中
    result[key1] = value1

# 遍历dict2的键值对
for key2, value2 in dict2.items():
    # 判断键是否已经存在于result中
    if key2 in result:
        # 将值相加，并更新result中该键对应的值
        for sub_key, sub_value in value2.items():
            if sub_key in result[key2]:
                result[key2][sub_key] += sub_value
            else:
                result[key2][sub_key] = sub_value
    else:
        # 直接将键值对添加到result中
        result[key2] = value2

print(result)

{'a': {'x': 6, 'y': 2, 'z': 6}, 'b': {'x': 3, 'y': 4}, 'c': {'x': 7, 'y': 8}}