How do I get the name of an SQLAlchemy object’s primary key?

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.