Serialising an Enum member to JSON

python

enum

serialization

json

byNikita Barsukov·Mar 6, 2025

Transform an Enum to JSON by implementing a custom encoder that outputs Enum values. Leverage Python's json module, inheriting from JSONEncoder:

import json
from enum import Enum

# Our very own Enum
class Color(Enum):
    RED = 'red'
    GREEN = 'green'
    BLUE = 'blue'

class EnumEncoder(json.JSONEncoder):
    def default(self, obj):
        # Let me be frank, or rather let me be Enum
        return obj.value if isinstance(obj, Enum) else super().default(obj)

# And...Action!
json_str = json.dumps(Color.RED, cls=EnumEncoder)

This snippet generates a JSON string from an Enum member, by transforming the Enum's value into its literal value, ensuring a "no surprises" serialization.

Safeguarding uniqueness with Enums

Keep your Enumerators unique and avoid "seeing double". Apply @unique decorator to your Enums to prevent value collisions.

from enum import Enum, unique

@unique
class UniqueColor(Enum):
    RED = 1
    GREEN = 2
    BLUE = 3

Choosing your serialization flavor

If a string representation is your cup of tea, use json.dumps with default=str. A handy shortcut for Python 3.7+ users:

json_str = json.dumps(UniqueColor.RED, default=str)  # "1" is the output, straight and simple

And for those favoring integers, use IntEnum to create a smooth serialization experience:

from enum import IntEnum

class Color(IntEnum):
    RED = 1
    GREEN = 2
    BLUE = 3

json_str = json.dumps(Color.RED)  # Outputs "1", a neat integer

The lambda magic

For a clean inline transformation, embed a lambda function in json.dumps to ensure Enum value representation:

json_str = json.dumps(Color.RED, default=lambda x: x.value if isinstance(x, Enum) else str(x))  # for the minimalist in you

Decoding Enums from JSON

The `as_enum` function

To switch things back and decode JSON to Enum, create a nifty function, as_enum, for smooth reconversion:

def as_enum(enum_class, value):
    return enum_class(value) if value in enum_class._value2member_map_ else value

color = as_enum(Color, 'RED')  # Unmasks itself as Color.RED