使用OrderedDict进行SQLAlchemy关系（）？

Question

Is it possible to tell SQLAlchemy to use OrderedDict for the relationship storage? I'm only familiar with attribute_mapped_collection , but that's unordered.

Answer 1

There's an example of this in the docs:

from sqlalchemy.util import OrderedDict
from sqlalchemy.orm.collections import MappedCollection

class NodeMap(OrderedDict, MappedCollection):
    """Holds 'Node' objects, keyed by the 'name' attribute with insert order maintained."""

    def __init__(self, *args, **kw):
        MappedCollection.__init__(self, keyfunc=lambda node: node.name)
        OrderedDict.__init__(self, *args, **kw)

Usage is simply:

foo = relationship(..., collection_class=NodeMap)