SQLAlchemy Enum type based on Integer indices, for better storage efficiency over the default Enum type.

mytypes.py

"""
SQLAlchemy Enum type based on Integer indices.
"""
from sqlalchemy import types

class Enum(types.TypeDecorator):
    impl = types.Integer

    def __init__(self, value_map, strict=True, *args, **kw):
        """Emulate Enum type with integer-based indexing.

        value_map:
            An integer_id:name dictionary of possible values, or a list of value
            names (which gets converted to corresponding index numbers starting from 1).
        strict:
            Assert that data read from the database matches with the expected
            valid value definitions.
        """

        self.strict = strict

        if isinstance(value_map, list):
            value_map = dict((k+1,v) for k,v in enumerate(value_map))

        # Enum lookup indices
        self.id_lookup = value_map
        self.name_lookup = dict((v,k) for k,v in value_map.iteritems())

        super(Enum, self).__init__(self, *args, **kw)

    def process_bind_param(self, value, dialect):
        id = self.name_lookup.get(value)
        if not id:
            raise AssertionError("Name '{0}' is not one of: {1}".format(value, self.name_lookup.keys()))
        return id

    def process_result_value(self, value, dialect):
        name = self.id_lookup.get(value)
        if self.strict and not name:
            raise AssertionError("Id '{0}' is not one of: {1}".format(value, self.id_lookup.keys()))
        return name

    def copy_value(self, value):
        "Convert named value to internal id representation"
        return self.name_lookup.get(value)

Are you still using this? It'll be a good addition to https://github.com/kvesteri/sqlalchemy-utils
Although it is somewhat similar to ChoiceType there.