sqlalchemy - automatically truncate string

gistfile1.txt

import sqlalchemy.types as types


class LimitedLengthString(types.TypeDecorator):
    impl = types.String

    def process_bind_param(self, value, dialect):
        return value[:self.impl.length]

    def copy(self, **kwargs):
        return LimitedLengthString(self.impl.length)


class MyModel:
    __tablename__ = 'my_model'

    id = Column(Integer, primary_key=True, autoincrement=True)
    name = Column(LimitedLengthString(40), nullable=False, unique=True)