[Bf-python] Proposed BPyAPI Additions.

[Ken Hughes]

Campbell Barton wrote:
> Im not keen on this at the moment,
> having reset would only help in cases where users had the same PyObject
> 
> # eternal loops like this would still be possible unless we store some 
> data in the Blender scene
> for ob in scn.objects:
>    scn.objects.new(ob.data)
> 
> the way the iterator currently works is......
> 
> iter is a BASE pointer, initialized as  NULL, if your loop on objects it 
> will to a Base.
> when your finished iterating its set back to NULL.
> 
> if your loop over the objects and the PyTypes iter value is not NULL,  
> then a copy of the scm.objects is returned with iter set to NULL.
> Without this... the following would not work.
> 
> obs = scn.objects
> for ob1 in obs:
>  for ob2 in obs:
>    print ob1, ob2

I guess I see the problem you're talking about: there are two different 
iterators even though to the user there is only one sequence ("obs"). 
The internal loop is a different iterator PyObject.

I'd vote for one of these two solutions:
(1) don't allow add or remove in iterators, period
(2) allow users to add or remove at their own risk, particularly 
remove().  Adding can cause and enless loop, removing may mean you crash 
(if you remove the object the iterator is pointing at).

(1) seems a lot more safer, so if a user wants to add an object to the 
scene they should add to a list, then add the list later:

obs = scn.objects
l = []
for ob1 in obs:
    ... l.append(ob2)
for ob1 in l:
    obs.new(l)

> I think its fair to say-
> "Dont add objects as you loop over them"

Uh, yeah, that's good too :-)

Ken