An enumerated type (enum) attribute for pynamodb

enum_attribute_pynamodb.py

from pynamodb.models import Model
from pynamodb.constants import STRING
from pynamodb.attributes import UnicodeAttribute

ENUM = ('FOO', 'BAR', 'BAZ') 


class EnumUnicodeAttribute(UnicodeAttribute):
    """
    An enumerated unicode attribute
    """
    attr_type = STRING

    def serialize(self, value):
        """ Raises ValueError if input value not in ENUM, otherwise continues as parent class """
        if value not in ENUM:
            raise ValueError(f"{self.attr_name} must be one of {ENUM}, not '{value}'")
        else:
            return UnicodeAttribute.serialize(self, value)


class Task(Model):
    """
    A schema for an object in the Task table
    """
    class Meta:
        table_name = 'task-table'
    status = EnumUnicodeAttribute()

This now exists in pynamodb-attributes. See: https://github.com/lyft/pynamodb-attributes/blob/master/pynamodb_attributes/unicode_enum.py