Question

I just want to programatically determine the name of an SQLalchemy model’s primary key.

Answer 1

If using SQLAlchemy version 0.8 or later, you should use the runtime inspection API.

If the model class is User and the sole primary key is id,

>>> from sqlalchemy.inspection import inspect
>>> inspect(User).primary_key[0].name
'id'

If the model class is User and there are many primary keys,

>>> from sqlalchemy.inspection import inspect
>>> [key.name for key in inspect(User).primary_key]
['id', 'name']

If using SQLAlchemy version less than 0.8, you should use the class_mapper() function instead.

>>> from sqlalchemy.orm import class_mapper
>>> class_mapper(User).primary_key[0].name
'id'

In this case, the inspect() function and the class_mapper() function return the same object, but using inspect() is more future-proof.