They could also have done default=uuid.uuid4 to have a new id each time, or default=lambda : str(uuid.uuid4()). It's not really related to whether or not it's a

They could also have done default=uuid.uuid4 to have a new id each time, or default=lambda : str(uuid.uuid4()). It's not really related to whether or not it's a database default. It seems quite unfair to place the blame on SQLAlchemy here, or even Python. Even a statically typed language wouldn't prevent this kind of issue - the author of the code is the only person who can decide when they mean "use this exact string each time" or "use this function to give me a new string each time". I suppose a column description API could follow the dataclass style definition, with different argument names for default and default_func. That would (I think) prevent this from happening.