How can I construct an enum.Enum from a dictionary of values?

Question

I'd like to generate some types at runtime from a config file. For simplity, let's assume I already have the data loaded as a python dictionary:

color_values = dict(RED = 1, YELLOW = 2, GREEN = 3)

How can I transform this into the type (using enum)

class Color(enum.Enum): RED = 1 YELLOW = 2 GREEN = 3

The following doesn't work

def make_enum(name, values): return type(name, (enum.Enum,), values)

>>> Color = make_enum('Color', color_values) AttributeError: 'dict' object has no attribute '_member_names'

You should probably use an OrderedDict rather than a regular dict. — user2357112
– user2357112, Commented Nov 15, 2017 at 4:04
@IoannisFilippidis: In my defense, I remembered that question as being one pre-enum.Enum, which would just tell me to use it. Of course, you're right that it shows the example I needed there. — Eric
– Eric, Commented Nov 15, 2017 at 4:10

user2357112 · Accepted Answer · 2017-11-15 04:09:46Z

Color = Enum('Color', color_values)

Tada! There's a provided API for that. You can also give it an iterable of name-value pairs, or an iterable of just names (in which case the values will be auto-filled starting from 1), or a whitespace- or comma-separated string of names (which will also auto-fill values).

Eric · Accepted Answer · 2017-11-15 03:52:03Z

Here's one super-hacky approach that seems to work:

def make_enum(name, values): _k = _v = None class TheEnum(enum.Enum): nonlocal _k, _v for _k, _v in values.items(): locals()[_k] = _v TheEnum.__name__ = name return TheEnum

We have to use nonlocal there to stop Enum complaining about the keys k and v being duplicated.

Eric · Accepted Answer · 2017-11-15 04:13:02Z

And another one that chooses to hit the metaclass internals instead:

def make_enum(name, values): meta = type(enum.Enum) bases = (enum.Enum,) dict = meta.__prepare__(name, bases) for k, v in values.items(): dict[k] = v return meta(name, bases, dict)

Or with less __dunder__:

import types def make_enum(name, values): def _update(d1, d2): for k, v in d2.items(): d1[k] = v # calls __setitem__ return types.new_class(name, (enum.Enum,), None, lambda ns: _update(ns,values))

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