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A small library for adding total orderings to enums

Project description

ordered_enum

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ordered_enum is a small library for adding (total) orderings to enum.Enums.

It provides two ordering behaviors:

  • ordered_enum.OrderedEnum: total ordering by definition
  • ordered_enum.ValueOrderedEnum: "total" ordering by member values

Installation

ordered_enum requires Python 3.6 or newer.

pip3 install ordered_enum

Usage

To use ordered_enum, just use OrderedEnum or ValueOrderedEnum as your parent class:

from ordered_enum import OrderedEnum


class State(OrderedEnum):
    Disabled = 4
    Loaded = 3
    Waiting = 2
    Running = 1
    Dead = 0


assert(State.Disabled < State.Loaded)
assert(sorted([State.Dead, State.Waiting]) == [State.Waiting, State.Dead])

OrderedEnum doesn't require @enum.unique (or unique values at all); it uses the order of definition to impose an ordering between members.

If you'd like to impose an ordering based on member values, you can use ValueOrderedEnum instead:

import enum
from ordered_enum import ValueOrderedEnum


@enum.unique
class State(ValueOrderedEnum):
    Disabled = 4
    Loaded = 3
    Waiting = 2
    Running = 1
    Dead = 0


assert(State.Disabled > State.Loaded)
assert(sorted([State.Waiting, State.Dead]) == [State.Dead, State.Waiting])

ValueOrderedEnum does require unique values, which can be enforced via @enum.unique. Failing to make a ValueOrderedEnum's values unique will result in a silently broken ordering.

Caveats

As mentioned above, ordered_enum.OrderedEnum provides an ordering of enum values based on their order of definition in the class. This means that:

  1. Enum values doesn't have to be unique for ordered_enum to work
  2. Enum values can be heterogeneously typed
  3. Moving enum values around changes their ordering

Therefore, you should either not depend on a specific ordering or ensure that your order of definition is the order you'd like.

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