It has to be a string, so you can have:
JSON is a format for serialising object data. It doesn't really care or know about Python types, the json package tries to translate whatever object you pass
json.dumps() into a string form via a
conversion table that only supports some types (see doc below).
因为有些人 comments 说，显式地将字符串传递给
json.dumps(obj, *, skipkeys=False, ensure_ascii=True, check_circular=True, allow_nan=True, cls=None, indent=None, separators=None, default=None, sort_keys=False, **kw) Serialize obj to a JSON formatted str using this conversion table. The arguments have the same meaning as in dump().
Note Keys in key/value pairs of JSON are always of the type str. When a dictionary is converted into JSON, all the keys of the dictionary are coerced to strings. As a result of this, if a dictionary is converted into JSON and then back into a dictionary, the dictionary may not equal the original one. That is, loads(dumps(x)) != x if x has non-string keys.
taken from the official docs here: https://docs.python.org/3/library/json.html