How to properly use association_proxy and ordering_list together with SQLAlchemy

Question

Based on some posts on the SQLAlchemy Google Group:

https://groups.google.com/forum/#!topic/sqlalchemy/S4_8PeRBNJw https://groups.google.com/forum/#!topic/sqlalchemy/YRy

Answer 1

sooo close ;-)

Please read Creation of New Values secion of association_proxy extension.
In order to make your code work, you can either

Option-1: add the following constructor to UserImage class:

def __init__(self, image):
    self.image = image

or

Option-2: override the default creator with your function:

images = association_proxy('_images', 'image',
    creator=lambda _i: UserImage(image=_i),
    )

I personally favor the latter.