如何按字符拆分嵌套字典中的值

def split_dict_value(dictionary):
    result = {}
    for key, value in dictionary.items():
        if isinstance(value, dict):
            nested_result = split_dict_value(value)
            for nested_key, nested_value in nested_result.items():
                result[key + '.' + nested_key] = nested_value
        else:
            for i, char in enumerate(str(value)):
                result[key + '[' + str(i) + ']'] = char
    return result

input_dict = {
    'key1': {
        'nested_key1': 'value1',
        'nested_key2': 'value2'
    },
    'key2': 'value3'
}

output_dict = split_dict_value(input_dict)
print(output_dict)

{
    'key1.nested_key1[0]': 'v',
    'key1.nested_key1[1]': 'a',
    'key1.nested_key1[2]': 'l',
    'key1.nested_key1[3]': 'u',
    'key1.nested_key1[4]': 'e',
    'key1.nested_key2[0]': 'v',
    'key1.nested_key2[1]': 'a',
    'key1.nested_key2[2]': 'l',
    'key1.nested_key2[3]': 'u',
    'key1.nested_key2[4]': 'e',
    'key2[0]': 'v',
    'key2[1]': 'a',
    'key2[2]': 'l',
    'key2[3]': 'u',
    'key2[4]': 'e',
    'key2[5]': '3'
}