SQLAlchemy Get Raw SQL Value from TypeDecorator

Question

I have defined the following custom type for sqlalchemy:

class EnumColumnType(TypeDecorator):
    impl = Integer

    def __init__(self, enum, *args, **kwargs):
        self.enum = enum
        super(EnumColumnType, self).__init__(*args, **kwargs)

    def process_bind_param(self, value, dialect):
        if value is None:
            return None
        return value.value

    def process_result_value(self, value, dialect):
        if value is None:
            return None
        return self.enum(value)

    @property
    def python_type(self):
        return int

Essentially, it encapsulates a python enum and writes it back as an integer to the sql table.

Assume I have the following enum defined:

class Bar(Enum):
    foo = 1
    bar = 2
    baz = 3

Assume I have a model as follows:

class Foo(base):
    enum = Column(EnumColumnType(Bar))
    id = Column(Integer, primary_key=True)

If I have an instance of Foo ie row = Foo(enum=Bar.baz) , is it possible for me to get the sql type of row.enum ? Currently, row.enum correctly evaluates to Bar.baz , but I would like to get 3, the value being written to the sql table. Is it possible to do this? Note that the EnumColumnType , Bar and Foo are defined correctly since sqlalchemy correctly persists rows to the table.

Answer 1

I'm not an SQLAlchemy user, but I can say that the point of Enum is to provide a textual representation of a unique value.

From your description I think you would be best served by an IntEnum which, while still having a textual representation of Bar.foo or Bar.baz would still be directly usable as the int 1 or 3