I think it would be easier to use your dict directly.
data = {
    "1": {"b": 1} 
}
some_value = data["1"]["b"]
If you want to use SimpleNamespace you need to replace 1 with something like _1 to be able to use something like x._1.b because x.1.b raises a syntax error.
This can be done by recursively converting your dict to a SimpleNamespace object and inserting _ in all keys starting with a number.
def dict_to_namespace(d):
    return SimpleNamespace(
        **{
            (f"_{k}" if k[0].isdecimal() else k): (
                dict_to_namespace(v) if isinstance(v, dict) else v
            )
            for k, v in d.items()
        }
    )
x = dict_to_namespace(data)
some_value = x._1.b
Note: this will lead to errors if your dict/json keys contain special characters (spaces, dashes etc.)