Data Enums

An alternative to the built-in Python enum implementation. Supports Python 3.11+, including free-threaded Python (3.14t).

Data enums allow you to:

• Define enum members with associated data using type hints
• Enforce unique constraints on attributes
• Look up members by name or unique attribute values
• Filter members by any attribute
• Use pure enums without any data attributes

Usage

Install via PyPI:

pip install data-enum

Basic example

from typing import Annotated

from data_enum import DataEnum, UNIQUE, UniqueTogether

class Currency(DataEnum):
    __members__ = ("USD", "EUR", "GBP")

    symbol: str
    name: str
    code: Annotated[str, UNIQUE]

Currency.USD = Currency(symbol="$", name="US Dollar", code="USD")
Currency.EUR = Currency(symbol="€", name="Euro", code="EUR")
Currency.GBP = Currency(symbol="£", name="Pound Sterling", code="GBP")

Access data on members

Currency.USD.name      # 'US Dollar'
Currency.EUR.symbol    # '€'
str(Currency.USD)      # 'USD'
repr(Currency.USD)     # 'Currency.USD'

Look up members by name

Currency.get("USD")                          # Currency.USD
Currency.get("MISSING", default=None)        # None
Currency.get("MISSING", default=Currency.USD)  # Currency.USD

Look up by unique attribute

Currency.get(code="EUR")                          # Currency.EUR
Currency.get(code="MISSING", default=Currency.USD)  # Currency.USD

Filter by any attribute

Currency.filter(symbol="$")  # frozenset({Currency.USD})
Currency.filter(symbol="₿")  # frozenset()

Compare and hash

Currency.USD == Currency.EUR  # False
Currency.USD == Currency.USD  # True

{Currency.USD, Currency.EUR}  # works in sets
{Currency.USD: "dollar"}      # works as dict keys

Default values

Use standard Python default syntax to make attributes optional:

class Currency(DataEnum):
    __members__ = ("USD", "EUR", "GBP")

    symbol: str
    name: str
    code: Annotated[str, UNIQUE]
    active: bool = True

Currency.USD = Currency(symbol="$", name="US Dollar", code="USD")           # active=True
Currency.EUR = Currency(symbol="€", name="Euro", code="EUR", active=False)  # active=False

Defaults work with Annotated types too:

tag: Annotated[str, UNIQUE] = "none"

Unique-together constraints

Use UniqueTogether("group_name") to enforce that a combination of attributes is unique:

class State(DataEnum):
    __members__ = ("CA_US", "TX_US", "ON_CA", "BC_CA")

    country: Annotated[str, UniqueTogether("location")]
    code: Annotated[str, UniqueTogether("location")]
    name: str

State.CA_US = State(country="US", code="CA", name="California")
State.TX_US = State(country="US", code="TX", name="Texas")
State.ON_CA = State(country="CA", code="ON", name="Ontario")
State.BC_CA = State(country="CA", code="BC", name="British Columbia")

Individual attributes can repeat (country="US" appears twice), but the combination must be unique. Look up by passing all group attributes to get():

State.get(country="US", code="CA")  # State.CA_US
State.get(country="CA", code="ON")  # State.ON_CA

UniqueTogether works alongside UNIQUE and defaults:

class Place(DataEnum):
    __members__ = ("A", "B")

    country: Annotated[str, UniqueTogether("location")]
    code: Annotated[str, UniqueTogether("location")]
    full_name: Annotated[str, UNIQUE]
    active: bool = True

Type checker support

DataEnum uses PEP 681 (@dataclass_transform) so type checkers (mypy, pyright, ty) understand the constructor signature generated from your annotations:

Currency(symbol="$", name="US Dollar", code="USD")  # type checker knows these kwargs
Currency(symbol="$")                                  # type checker flags missing args

No-data enums

class Direction(DataEnum):
    __members__ = ("NORTH", "SOUTH", "EAST", "WEST")

Direction.NORTH = Direction()
Direction.SOUTH = Direction()
Direction.EAST = Direction()
Direction.WEST = Direction()

All members (in declaration order)

Currency.members  # (Currency.USD, Currency.EUR, Currency.GBP)

Thread safety

DataEnum is safe for use with free-threaded Python (3.14t, no-GIL). All runtime operations — get(), filter(), attribute access, iteration — are read-only on frozen data structures. Define your enum members at module load time (the normal usage pattern), and they are safe to access concurrently from any number of threads.

Safety

Members are immutable:

Currency.USD.name = "Bitcoin"  # raises AttributeError

Duplicate unique values are rejected:

Currency.GBP = Currency(symbol="£", name="Pound", code="EUR")  # raises ConfigurationError

All declared members must be assigned before use:

class Color(DataEnum):
    __members__ = ("RED", "BLUE")
    name: str

Color.RED = Color(name="Red")
Color.get("RED")  # raises ConfigurationError (BLUE not yet assigned)

Development

Set up the development environment:

make setup
source .venv/bin/activate

Run the full pipeline:

make

License

Licensed under the Apache License, Version 2.0.