如何基于一个key python合并字典列表

def merge_dicts(dicts, key):
    merged_dict = {}
    for d in dicts:
        if key in d:
            if key in merged_dict:
                merged_dict[key].extend(d[key])
            else:
                merged_dict[key] = d[key]
        else:
            merged_dict.update(d)
    return merged_dict

dicts = [{'a': [1, 2, 3]}, {'b': [4, 5, 6]}, {'a': [7, 8, 9]}, {'c': [10, 11, 12]}]
key = 'a'
merged_dict = merge_dicts(dicts, key)
print(merged_dict)

{'a': [1, 2, 3, 7, 8, 9], 'b': [4, 5, 6], 'c': [10, 11, 12]}