On 10/16/2010 1:55 PM, Michael Bayer wrote:
On Oct 16, 2010, at 2:03 PM, Michael Hipp wrote:
On 10/16/2010 12:52 PM, Michael Bayer wrote:
On Oct 16, 2010, at 1:02 PM, Michael Hipp wrote:
On 8/24/2010 9:47 PM, Michael Bayer wrote:
Michael Hipp wrote:
How do I make a copy of an orm object such that modifications to the
copy do not affect the original?
The mapped object has a member "_sa_instance_state" that you basically
don't want to transfer to your new object. You want it to have its own
"_sa_instance_state" and this comes from calling the plain constructor,
which the "copy" module, if that's what you're using, does not use. You
also want to set attributes normally, not populating __dict__ directly.
So just basically don't use the "copy" module.
x = MyObject()
for a in dir(myoldobject):
if not a.startswith('_'):
setattr(x, a, getattr(myoldobject, a))
Resurrecting an old thread ...
I'm just now getting around to try this but I'm finding out it doesn't really
work like I'd hoped.
As soon as 'getattr' hits a column with a ForeignKey it immediately tries to
autoflush INSERT 'x'. But 'x' is only half-baked and not ready to be saved.
In fact, I don't ever want to save 'x', and I especially don't want to INSERT
it. It would be a duplicate of 'myoldobject'.
Is there a way to copy an orm object and tell it "don't ever save this I just want
to keep it around to look at"?
Alternatively I can just copy all the attributes to a dict(), but that's a bit
messy.
dont put it in the Session.
That makes sense. But how do I not do that? As in your example code above I'm
not adding it to a session, at least not intentionally.
don't call Session.add(). the code above doesn't add to a session unless
you're using some special extensions like Session.mapper.
As shown exactly in the code above, I do *not* call Session.add().
It appears to be doing the add when it hits the ForeignKey field. Then it not
only does an add it also attempts an INSERT (which thankfully fails since the
object is not ready to be saved).
Michael
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