Hey,
I had trouble deepcopying model instances that use attribute mapped
collection classes. I'm aware that copying an instance implies a
certain use case with a better solution - I accidentally hit this
error when I had an instance as an attribute on an object I was
deepcopy()ing. The following example fails with "TypeError: attrgetter
expected 1 arguments, got 0".
Is there a way to remedy the situation a bit so the deepcopy doesn't
fail so spectacularly?
Thanks,
N
from sqlalchemy import create_engine, Column, ForeignKey
from sqlalchemy.ext.declarative import declarative_base
from sqlalchemy.orm import scoped_session, sessionmaker, relationship
from sqlalchemy.orm.collections import attribute_mapped_collection
from sqlalchemy.types import Integer, String
import copy
engine = create_engine('sqlite:///:memory:', echo=True)
Base = declarative_base(bind=engine)
Session = scoped_session(sessionmaker(bind=engine))
class Note(Base):
__tablename__ = 'notes'
keyword = Column(String, primary_key=True)
item_name = Column(String, ForeignKey('items.name'))
class Item(Base):
__tablename__ = 'items'
name = Column(String, primary_key=True)
notes = relationship(Note,
collection_class=attribute_mapped_collection('keyword'))
Base.metadata.create_all()
item = Item(name='Foo')
note = Note(keyword='Bar')
item.notes.set(note)
Session.commit()
assert item.notes['Bar'] is note
copy.deepcopy(note) # Passes
copy.deepcopy(item) # Fails
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