from decimal import Decimal as D
import sqlalchemy.types as types

class SqliteNumeric(types.TypeDecorator):
    impl = types.String
    def load_dialect_impl(self, dialect):
        return dialect.type_descriptor(types.VARCHAR(100))
    def process_bind_param(self, value, dialect):
        return str(value)
    def process_result_value(self, value, dialect):
        return D(value)

# can overwrite the imported type name
# @note: the TypeDecorator does not guarantie the scale and precision.
# you can do this with separate checks
Numeric = SqliteNumeric
class T(Base):
    __tablename__ = 't'
    id = Column(Integer, primary_key=True, nullable=False, unique=True)
    value = Column(Numeric(12, 2), nullable=False)
    #value = Column(SqliteNumeric(12, 2), nullable=False)

    def __init__(self, value):
        self.value = value