将枚举成员序列化为 JSON

发布于06月30日

如何将Python Enum成员序列化为JSON，以便将生成的JSON反序列化回Python对象？

For example, this code:

from enum import Enum    
import json

class Status(Enum):
    success = 0

json.dumps(Status.success)

导致错误的原因:

TypeError: <Status.success: 0> is not JSON serializable

我怎样才能避免呢？

推荐答案

如果您想将任意enum.Enum个成员编码为JSON，然后进行解码

PUBLIC_ENUMS = {
    'Status': Status,
    # ...
}

class EnumEncoder(json.JSONEncoder):
    def default(self, obj):
        if type(obj) in PUBLIC_ENUMS.values():
            return {"__enum__": str(obj)}
        return json.JSONEncoder.default(self, obj)

def as_enum(d):
    if "__enum__" in d:
        name, member = d["__enum__"].split(".")
        return getattr(PUBLIC_ENUMS[name], member)
    else:
        return d

The as_enum function relies on the JSON having been encoded using EnumEncoder, or something which behaves identically to it.

The restriction to members of PUBLIC_ENUMS is necessary to avoid a maliciously crafted text being used to, for example, trick calling code into saving private information (e.g. a secret key used by the application) to an unrelated database field, from where it could then be exposed (see https://chat.stackoverflow.com/transcript/message/35999686#35999686).

Example usage:

>>> data = {
...     "action": "frobnicate",
...     "status": Status.success
... }
>>> text = json.dumps(data, cls=EnumEncoder)
>>> text
'{"status": {"__enum__": "Status.success"}, "action": "frobnicate"}'
>>> json.loads(text, object_hook=as_enum)
{'status': <Status.success: 0>, 'action': 'frobnicate'}