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

I just want to programatically determine the name of an SQLalche开发者_如何转开发my model'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.

If class is "User", and there is just 1 primary key, do this*:

User.__mapper__.primary_key._list[0].name

^*_{Moved from the question.}

Assuming the declarative model class is User,

>>> list(User.__table__.primary_key)[0].name
'id'

Or for Membership which has a composite primary key

>>> [pk.name for pk in Membership.__table__.primary_key]
['user_id', 'group_id']