These sometimes use a lot of dynamic modification, such as adding implicit ID fields or adding properties to navigate a relationship with another type that is defined in code only from the other side.
It can also be awkward to deal with “not null” database fields if the way the ORM model classes are defined means fields are nullable as far as the Python type hints are concerned, yet the results of an actual database query should never have a null value there. Guarding against None every time you refer to one of them is tedious.
I’m not exactly the world’s loudest advocate for ORMs anyway, but on projects that also try to take type safety seriously, they do seem to be a bit of a dark corner within the Python ecosystem.
The approach I have found to work is isolate the logic which deals with ORM models, and convert them to/from typed models (eg pydantic) at the function boundary.
with sqlalchemy mapped_column, its less of an issue. django, otoh, seems too much magic for static type. (happy to be proven wrong).
ORMs have entered the chat…
These sometimes use a lot of dynamic modification, such as adding implicit ID fields or adding properties to navigate a relationship with another type that is defined in code only from the other side.
It can also be awkward to deal with “not null” database fields if the way the ORM model classes are defined means fields are nullable as far as the Python type hints are concerned, yet the results of an actual database query should never have a null value there. Guarding against None every time you refer to one of them is tedious.
I’m not exactly the world’s loudest advocate for ORMs anyway, but on projects that also try to take type safety seriously, they do seem to be a bit of a dark corner within the Python ecosystem.